Im with my best friend in a friendship for about 8 months and from along time I have a feeling that I like her but I didn't tell her that because I was afraid to loose her! But before few days she told me that she has a boyfriend now I really was shocked and I cried! I told her that I like her and I was afraid to say that from along time! She told me she doesn't want to ruin her relationship with her boyfriend and I'm just a friend! I really really love her I always think about her every I cry! Please give me a solution! I will never give up

The solution... Give up.

If you press her to be in a relationship with you all you will do is push her away.

Not only does she have a boyfriend but she also told you she just wants to be friends.

I have been in a similar situation recently but in reverse. A very good friend of mine told me that he was interested in me romantically. I don't have any interest in him in that way but I love him to death as a friend. I flat out told him so and now we are just back to being friends.
If he hadn't respected my wishes and kept pushing for me to go out with him I would have simply avoided speaking to him. I was flattered that he thought of me that way, but also a little uncomfortable having to break the news to him. Having to repeatedly tell him I was not interested would have killed our relationship as friends.

Respect her wishes, there are plenty more fish in the sea.