I slept with my best friend now I don't know what to do.
Why did you sleep with her?
I just wanted to have fun with her and it sort of just happened.
You might ruin your relationship with them you need to be careful about things like that. It would be bad to lose a friend you had for so long.
All I did is to deflower her.
It adds a whole new complication into the friendship and should be avoided. You can't have it both ways.