I used to be friendly with her, and all of a sudden this happened.

I first met her last year, that time I had Autism and was bullied by my classmates a lot. She used to make me feel better whenever I'm crying after getting bullied.

After being healed, unexpectedly,that is when she and I started to become friends. We text to each other almost every day, we always do school projects together. She said "we're like sisters, I'm so happy I get to know you".

This year, she rarely uses her computer because of getting an average grade last year. We didn't text to each other as much as before and we didn't chat to each other that often.

Now, what I see is that she is always hanging out with another classmate (whom I am always jealous of), no matter what SHE asks to my best friend, my best friend would make a big reaction and laugh. But when I ask her, she would either just say it and make no serious reactions or just simply say "oh, so?".

Even when we needed to do group projects, she doesn't want me to join in the group and asked me to move onto another group, since I was unlucky and got kicked out by many other classmates, she let me join in the group but I'm knew that she wouldn't let me do anything at all.

Although I still have another friend and hang out with her a lot as well, I'm still very scared about losing my closest friend, things are still not the same.

My parents asked me why I didn't contact her recently, I lied to them and said, "We're not friends anymore, but I'm totally over it."

I didn't tell anybody the truth yet, I just don't when them to be worried about me. I don't want to express it to my closest friend either, otherwise she might turn selfish and discriminate me.

How can I solve this problem? I can't have this Autism sickness again. What should I do?

Do you mean depression or some other condition? Autism does not come and go.
Have you tried talking to your friend?

Let this go. You are making too much of the human condition to change and pursue other options. Instead accept the change and make adjustments in your thinking of her, and others and be open to exploring your world.

Relationships, and friendships at any age can go through changes, and phases. Best friends come and go and we miss them, but we also let them do as they please as we also do as we please. I have always looked at it as a pleasure to have spent the time but things do change for whatever reasons.

How you cope, and deal with it is the important thing, and I see it as we never know when they will come back into our lives, so let this go for now and don't be stuck on feelings of disappointment and frustrations, given you have a new friend.

Do you mean depression or some other condition? Autism does not come and go.
Have you tried talking to your friend?
It's true that I had Autism, I've seen therapists before, the case was closed for a year ago.

Right now, I still can't let it go, I tried apologizing to her on the phone twice but she never replied. It's been a week and things are getting worse, I've been having nightmares lately.

I'm very confused now, I can't invite her to go out with me, I can't text her because she ignores it, and I've been having nightmares. I can't avoid it. I feel helpless and I don't know what to do...

I know you people are probably going to tell me to let it go, but I just can't.

Don't say you don't know what to do, because you do know exactly what you must do. You don't want to. You would rather make a perfect pest of yourself for nothing.

When you have tried to apologize to a person to no avail, then you leave it alone. She is not the only person in the world. Get out and make new friends. Choose to let this go.