I’m Afraid I Might Lose My Best Friend by Setting Boundaries

TL;DR:
I’ve been best friends with this girl since we were kids, and I truly love her like a sister. But lately, some red flags have started to show — including talking behind my back to my partner (now ex), making passive-aggressive comments, and shutting down when I try to be honest. I’m afraid that if I set boundaries or confront her, I might lose the friendship altogether. I need some advice.

I (19M) have been friends with a girl — let’s call her K (19F) — since we were 12 or 13. She’s been one of the realest people in my life: always there to make me laugh even during the hardest times, and someone who’s listened to me more times than I can count. She’s truly like a sister to me, and I love her with all my heart.

But… lately, some red flags have started to appear.

Last year, I was in a relationship with a guy — D. I introduced D to K, and for a while, the three of us formed a little friend group. It was nice… until something happened.

One day, D confessed that K had been calling him behind my back. Apparently, she asked him not to tell me about those calls — and during them, she would complain about me and mention things she disliked about me. I asked D for proof, so he confronted her via text and sent me screenshots. She admitted to everything, claiming she felt “betrayed” by him, called him a “terrible friend,” and said she wasn’t sure he “deserved” her friendship.

I called her to talk about it. The entire conversation, she was defensive — at one point even saying, “Are you done now?” I pushed a bit more and showed her the screenshots. That’s when she broke down in tears and finally opened up. She admitted she’d been bottling up her feelings for a long time, afraid that if she expressed anything, I’d stop being her friend. She apologized, I forgave her, and we moved on… or at least, I tried to.

The friendship between her and D didn’t survive. She did try to apologize to him too, but by that point, he was too hurt and didn’t give her another chance. I have my own thoughts about that choice — but that’s a whole other story.

Eventually, I ended up breaking up with D. When I told K, she confessed that she had stopped liking him completely after everything that happened. She told me the whole situation had been “his fault” and that it was “greatly exaggerated for what it was” — almost as if she was walking back everything she had once apologized for. I tried to ignore it.

I have an anxious attachment style. Since the breakup, I’ve finally started healing through therapy. I’ve been learning how to walk the fine line between protecting myself with healthy boundaries and still remaining open and sincere with the people I love. I mention this because… something happened with K again last week.

She posted a vague note on social media that said, “I hate when people take hours to answer me.” I asked her what it was about, and she told me she had met a guy at a party that she was actually interested in. They exchanged Instagram handles and started texting — but apparently, he took way too long to reply, sometimes up to 5 hours. While she waited for his answer, she saw him being active in other group chats they were both in. She was pretty annoyed by it.

I told her that, based on my own experience with relationships, she should just confront him directly — especially since it’s still early on and this could be a good opportunity to see if he’s really worth it. She replied that it would be “too embarrassing” to open up like that to someone. I tried to talk it through with her, but eventually she stopped replying.

I didn’t think much of it at first… until I realized she hadn’t answered anything I’d sent her for five days. So I asked what was going on.

She told me she was very annoyed at how I “told her she was wrong” for posting that vague note, saying it could’ve been about anyone — even though she had already told me it was about this specific guy. Then she added: “You also post stories about how much you miss your ex and how he was the love of your life, and I don’t say anything to you about it.”

That comment hit me hard. Especially because she’s been the person who’s listened to me the most during this whole healing process. It felt… personal.

I did apologize — I told her I was sorry for offering my opinion when she didn’t ask for it. But now I’m torn. A part of me really wants to confront her about these types of comments she makes when she’s angry… but another part is scared. Scared that if I do, I’ll realize my “best friend ever” isn’t exactly who I thought she was.

What should I do?

Any advice would be deeply appreciated. Thank you.