I (M18) and my best friend (F18) have been growing apart

I met this girl on an Internet forum around August 2015. I joined the forum's skype call and started interacting and talking to all of the members, making myself a part of the group. Though we were acquaintances, my relationship with this girl would only come to flourish in December, when we became best friends, or besties as she'd put it.

Throughout December and January, we did a lot of things. We talked every day for hours, she'd act extremely enthusiastic and animated around me, using a lot of emojis, she'd tell me every day she loved me and how special I was, that she loved me unconditionally, that I was irreplaceable, and so on. She would talk about her daily life, come to ask me for advice when she argued with her boyfriend, come for advice for ANY sort of problem actually, big or small. She told me her deepest secrets, stuff that she only ever told her BF and not even her parents or other friends knew. And likewise, I could confide in her with EVERY secret I had. Her boyfriend even got jealous of our relationship sometimes and ended up arguing with her because of it.

Suffice it to say that I ended up falling for her. During these two months, I was incredibly happy. I felt special, felt validated, felt loved, even if platonically, I was getting over my depression thanks to her existence. I decided to confess at the end of January, not because I expected anything to come out of it, since she had a bf, but because I thought she should know. She took it well, said she loved me a lot, but only platonically, and promised this wouldnt affect our friendship. But it did.

The following week I could barely get hold of her. A few days before the forum meet-up I decided to go to because of her, she sent me a text saying sorry for not talking to me, that she was busy and starting from now her full attention would be on me. The meet-up went well, but after that is where things started to go wrong. I would barely talk to her during February. She was busy with school and she was moving to a new home, so I never bothered her, but sometimes we would go 3 or 4 days without talking. She was also having a rough period with her boyfriend at this time, they broke up this month (and luckily at this point she would still come to me whenever they argued), so I cut her some slack. Towards the end of the month, I had a huge argument with her ex and another guy who liked her and this got to her ears, but we resolved it fairly quickly since it was our first discussion ever.

So February was a month where she was super busy and stressed out. But March was where things changed completely. She was on break, so no more excuses about being busy. Whenever I came to talk to her, she would act completely uninterested, she'd never use emojis when before she'd spam me with them, she never again told me she loved me or complimented me even if I told her. She was acting completely differently. And meanwhile she was flirting with other guys in the skype group and treating them the same way she treated me! So instead of keeping my composure, I confronted her about it. I asked if she was still mad because of what I did back in February, she said no but I insisted. I said she was being different and listed off what she used to do and what she doesnt anymore and she just said she was treating me the same way. This went on for the entire month, we kept arguing back and forth, until FINALLY she told me she was having some psychological issues she didnt want to share. Which not only means she lied about not treating me differently but it also meant sonething was VERY off because before she would share with me her DEEPEST secrets. She said it wasnt me, it was her, but thats BS, she was treating EVERYONE else the same or better. I asked her if she still considered me her best friend and still loved me and she avoided the questions, which tells me everything i need to know really.

We havent spoke in two weeks, the longest time EVER. Last time we did, she asked me why I left the skype call (I left to try and move on from her, but of course i didnt tell her this). I'm not initiating contact, I need to feel wanted in her life and presently I dont.

Even though I love her, I was perfectly content with my relationship with her as best friends. I'm not looking for a way to seduce her or a way to go back. I realized that I cant stay friends with her, not if I'll always act needy like I did during March. I'll always ask her to go back to the way she was when she obviously doesnt want to. Instead, I just want a reason for what she did, so that I can at least try to understand and stop feeling like shit, like Im unwanted and like I was used and disposed of, replaced. She already started acting weird back in February, so it's not like I'm the one who changed, it was her. What was it? Did she just lose interest in me as a friend? Did she have some kind of romantic interest that died out? Was the month where she was busy enough to make her forget me? I need to know why she singled me out and started treating me differently and she wont tell me.

Tl;dr she said she loved me but hasnt spoken to me in 2 weeks