The famous friend-zone

I just overthink too much about this, and I wanted to tell this to someone else, but I feel like I can’t say anything even to my parents.
One year ago I started the high school (I’m 15M), I met a girl (16F) that after one or two months I stated liking, for the entire year I was too shy to confess or even make our relationship stronger. After the June – September holidays (I’m a Brazilian that lives in Italy), our relationship got stronger cause she was “afraid” of walking down the street alone, so every day I went with her within her car. Then on April we had to travel with our school to France, everything went well (expect the food, but that’s another story), until the last night, when she argued with her boyfriend (to be clear, since I knew she was engaged I never tried anything), she was really sad, but I told her to not think too much and just relax, also because it was the last night of our trip. After we returned to the hostel, she invited me to her room, there were other our friends also, so we just chatted a little, I went to their room also because I was worried for her, cause she had told me that she has some problems with food, so she can’t eatich at home, but at least with me she eats normally, sometimes even too much hahaha, and sometimes she finished hurting herself, her boyfriend (17 M, he’s a 2008) got angry (btw what a stupid way to react to other’s problem), and she was worried about what he could do on himself, I fortunately managed to calm her and made her praise for the first time in her life, so on the way back I told her some of my experience with God (another story), and then did that at the hostel. She slept and I stood there with her, she on her bed, me next to her on the floor.
After that day she started to ask me for many advices, and I thought for the fist time of my life I could actually help someone.
While the time passed, I could just like her even more, I literally knew the other part of her life, not only the good, but also the bad things in it.
One day we were out with a friend (15M) and she asks to us if we liked someone, I said yes, and then she asked for him, I told her I thought he liked her, as he was acting in a way quite different of a time before. Some time after it we had a math test, and, as I am really good and like it, she asked for help, I went to her house after school, had lunch only we two together (her mum was in the room next to us), and I successfully made her study 20 minutes, she was happy as she had never been able to study like 5 minutes. After hers studies she wanted to go out, we sat on a bench and she asks: “How did I stopped to like to you?” (Literal translation from Italian). I don’t need to say that I had to confess, I didn’t want to give a bad advice, she just told me I deserved a person better than she, before I answer, Marcus (let’s call him like this) arrived and I wasn’t able to answer her, and I’m not being able to find a way to finally answer her or if I even have to.
Like one month ago she broke up with her boyfriend, she asked for help, I tried my best, but I’ve never thought that relationship was the better for her, she was really engaged with it, but he wasn’t, in fact he had already cheated on her, and finally, before the break up she went to his house, they had sex and he did a video of her, she gave the consence cause she didn’t want to lose him after 8 months together; after one day he broke up with her, he said he would delete the video, but anyone with at least one brain cell know that he probably haven’t deletd it.
When she told me about the video I was speechless, I mean, I was feeling so bad, I never felt that angry I guess, I was so furious that I could kill him.
Again, after a while, we organized a bowling night with our friends, there she told me she had feelings for Marcus, then they went to the bathroom (btw what a strange place) and confessed to each other.
The next day they had a date and he kissed her, one hour later I met her and she told me she understood that she wanted just to be friends with Marcus after the kiss, but didn’t know how to do it.
Two days after I receive a bomb, I discovered that the night after the bowling, while she got home, she put an other guy’s hand on her leg, and the they after the date showed to a football match holding an other guy’s hand, making 3 guys in three days
I felt really bad for her, I didn’t know what to say, for the fist time in a while I couldn’t give any advice, I felt so bad for her as what every our friend was thinking about her that I cried, but I cried in a way that I knew I had reach my limit, because I just couldn’t stop, at the moment I was in front of a Church of my town, where I go when I want to relax and stay alone, I had to go out home after discovered everything.
One week later (like one week ago from today), I realized that I felt bad for nothing (at least I think I was too immature), as the problem didn’t even had to do with me, so I’m just ignoring this fact, and even if I’m considered by everyone as the psychologist of the group, I can’t told her about this and lost my friendship, I just can’t.
Since I know I can’t be anything more than a best friend for her, I just want to see her as happy as the sun, even if talking to a friend (17 M, he’s 2007) I realized I’ll never be really happy seeing her with an other guy.
I also discovered in the bench’s day that she also liked me for a while the last year, but no one of us was brave to confess to the other, so I lost the opportunity of don’t let all these problems happen.

This is a short resume of all the last 2 years of my life in high school, I couldn’t handle it alone, but also couldn’t tell my parents or my friends, as the “psychologist of the group”, so I decided to finally use Reddit, I really want to be the better possible, not only for me, but also for her and my other friends

TL;DR; : This is a sample summary of the TLDR rule, just copy the text in gray box. Is this going the right way?