TLDR; My (F20) GF (F25) might be too attached to her best friend (F23) – and I don’t know what to do

Dear Reddit dwellers,
I am quite a new commer in the reddit sphere in regard to posting. I have been lurking around the site for quite a while now, however I never really had the urge to post – until now.

I apologize for a possibly longer post, but I need to get this out somewhere and get some opinions from people who hear this for the first time and are not biased (like eg. our friends).

I will try my best to reiterate the problem to the best of my ability so you all can grasp both of our sides a little bit better.

Now for the problem:

For some context I (F20) have been experiencing some relationship problems with my girlfriend (F25) recently. Let’s call my girlfriend Lena for clarity.

Lena and I have been together for 3 years approximately.
We had our bumps in the relationship. Neither of us had the ideal family background. My mother was controlling my every move, and she was adopted into a disfunctional family with a rather angry dad and a mom who doesn’t speak to her now.
We had a little bit of a money problem since neither of our parents were able to support us financially much. I started working as a cashier part-time, and she worked for some time teaching English part-time.

We experienced a lot of trauma and stress during this period. We had to pay her tuition – which was a lot of money – and at her current job her boss cut her hours and I worked my ass off at my part-time job to pay the tuition she needed (approx. 500€).
I’ve developed financial anxiety due to how miserable we were when we could barely afford anything following her tuition payment. She was still searching for a job atthis time and dealing with serious mental health issues. So I threw myself into work so we can afford to pay the bills, so she can rest a little – all while attending Uni. All this combined has effectively destroyed me. I got extremely tired and could barely focus or communicate with her. And since we were living apart from each other at that time our relationship – and we both suffered.

I worked like this for at least five months, she did get a job later, however they let her go due to some unfortunate incidents (truly just bad bad luck). This tanked her mental health. I kept up working for the both of us. Later we did end up finding new jobs in the same place and started working – now the both of us. This however did not last long since her state exams (idk if it is a common thing in other countries, here it is the exam that decides if you get a degree or not) were coming up and she had to study – so I went yet again, alone to work the entire month.
I just got so extremely tired because of all this that I started to doubt she will ever start working again.

Lena has a best friend (23F), whom I will adress as Emily for clarity. Lena and Emily grew very close during the three years. They refer to each other as sisters and consider themselves family. Emily has many health problems – and I mean that. Every allergy on the planet, other health issues that are serious. In conclusion she truly did not win the genetic lottery. She also has extremely severe trauma in many areas and a borderline abusive family.

Lena and I decided to open our relationship about half a year ago. I have always had sexual intimacy problems due to past trauma and sex just really was not my thing. I agreed to this open relationship thing because I couldn’t take seeing Lena unhappy and didn’t want her to limit herself because I had some issues. In conclusion, Lena started sometimes sleeping with Emily (I know that the sister thing is weird in this context and disturbs me). She praised it, said that she finally felt wanted and enjoyed it immensely. I convinced myself I was happy because she was happy, however I never really accepted this and it bothered me immensely.

Now to the problem at hand:

Lena and I finally moved in together to a small apartment in a calm area of the city. The move was – horror. The flat had not been used for quite some time and it needed MAJOR repairs. Everything just kept going wrong. We were stressed, we were arguing and everything was just really shitty and stressful. I kept up going to work because one of us had to and she stayed home renovating the flat. Another important detail is that the repairs, electronics, and all that comes from 3000€ that my parents saved up for me from my birth. All of this money went into this, which I do realize was a massively stupid decision, but it’s reality.
Lena and I have been arguing about this open relationship for about a week. I feel unhappy and unappreciated and alone in this relationship. She is constantly on the phone with Emily, and I mean constantly. Lena often was with Emily during the last six or so months due to her not working and having to pretend to her dad. I mean ‘every day’ often.
Emily had a big health scare a few days ago and Lena was with her constantly. Talking and calling her constantly. Emily is away at a family trip at the moment and she and Lena text constantly, call at least three to four times a day, Lena stays on call with Emily during the night in case she has nightmares so she can wake her up, ect. I feel this is too close for my comfort. They talk like me and my girlfriend talk. In that lovey-dovey way. I had a really good best friend, but it was never like this.
I brought this up to Lena and she said that Emily was the only one who stayed with her through her problems and never made her feel like a disappointment or an issue. Said that due to me she hates who she is and how now that she started to look out for herself everyone hates her. How she felt alone in the last two years. How I became a workaholic and distant and tired and how she felt alone and Emily was there. She mentioned that I agreed to open the relationship – which to be fair, I did. Lena will never let go of Emily as she has already confirmed that. And now I feel like a third wheel in my own relationship.

I feel as through Lena had gotten very emotionally attached to Emily, even though they both keep reassuring me that it’s only platonic and that Emily truly cares about both of us and wants us together. I don’t believe it is. I just think they maybe have hidden feelings neither of them realize or idk.
A few days ago Lena had asked me to go home for a few days next week so she and Emily can have a sleep over. I asked why I cannot be here and her reasoning was that if I will be there too she and Emily won’t enjoy the night since I have a problem with Emily. I felt thrown out of my home, naturally.
I have essentially started vilianizing Emliy due to all this and some previous similar encounters, even though she is really sweet and kind. But Lena took to her so hard that I can’t help but feel contempt. I just think that Emily is not a child or Lena’s partner and that she can take care of herself and seek out the professional help that she needs.
All this caused us to spiral and led to me noticing how Lena and Emily’s relationship makes me feel. I admit my wrongs, I was agressive and don’t know how to confront people or communicate well and relied on isolation and ignorance and just hoped this all would go away, but now my relationship is in crisis and I want to fix this.
I have mentioned this to my psychiatrist. She told me to set boundaries and tell Lena my feelings. I did and she said she will tell Emily and end this because she wants to work on us too. I have a sinking feeling she will choose Emily over me if it comes to it.

She is adamant that all three of us get together and talk it out. I am preparing what to say to the both of them and would like a few unbiased opinions.

I truly do love Lena, I just need to know what to say to her so I can express my opinions clearly and well.

Is it crazy or reasonable to think like this?
Could you give me some advice on what to say to Lena and Emily?