ok so I'm 15 with no mental problems, I joined this subreddit in order to get some help with it cause I really don't know what to do.
so me and friend have a really close relationship. we talk to each  other everyday. especially now with the Corona virus shit so everybody is staying at home. 
she has a very serious case of mental problems. she has trust issues, she is always depressed and feels bad, she has problem talking with people and she almost always likes to be alone. she recently stopped cutting herself. 
a few days ago I talked with her, and somehow are talk changed from casual talk to emotional and deep one. now this is where it gets interesting. this is what she told me:
"Maybe it will sound manipulative on my side, but at the start of the year i didn't planned on befriending anybody. I just wanted some peace, and if the opportunity comes to me, i will take it.
Then you came, and honestly I didn't think you will be my best friend, i just wanted to talk to you a little until you get bored of me and you stop. But you never stopped. And then you started to open up emotionally, and i panicked, so i built a persona that i thought will appeal to you, and i was right. But it kept going and going, and i can't do this anymore. I can't keep being fake like that. I planned that i will transition smoothly to being more myself, but i guess it blow up in my face huh?"
 she told me I'm too much touchy and emotional and nice she just can't keep up at that pace  and she feels bad when I type that I love her cause she just can't do it also. she feels bad when she is typing me that for some unknown reason. so I tried to help her to solve her problems, or at least those that involves me. but I fucked-up, I was so panicked and I wrote her that I can't help her no matter how much I want (which was the worst mistake I ever made) and she said that she is disappointed at me and lost her trust in me. she told me that befriending me only caused her harm, and that she wouldn't care if I leave her, she trusted me, she thought I was different from other friends that "betrayed" her. 
"its ok, i didn't excepted you to help me, I trusted you and I was wrong, from now on I won't tell you anything personal anymore until you regain my trust. which will take you a lot of time"
she wrote and I realized I fucked it all up. but the thing is she is really important to me and I can't just leave her like that. I must fix the damage I've done to her, so I told her I will try to find a solution to our problem, that I'm too nice and she can't keep up the pace. 
now this is where it gets even harder, I have a crush on her and she knows it. she is saying that I'm not her type and if I won't get over this crush our friendship will come to an end.

so reddit, I require your help. here is the problem in short: she doesn't trust me anymore, I'm too nice to her, I'm acting like a lover other then a best friend,  and she always feels bad.
Please help me redditors, as an Extrovert with no mental problems, I need to know how to help her

thanks for reading this, it means a lot to me