I put a diaper on my best friend while she slept, then put her hand in a warm bowl of water then left
Did you really put a diaper on her?
I put a diaper on her and I'm glad I did it because now she's no longer talking shit about me.
This is something you should not have done. It is bad for you to treat your friends this way. You could destroy the relationship.
It's funny how she doesn't care anymore. She knows that I am a prankster and I will do it again.
If she saw it as a prank and is not mad, consider that lucky.   Doing that again is strange and could be seen as harassment.  You should take it as a one time classic prank and quit while you are ahead.