Is it normal to be a girl and want to be with a girl?

I have a really close friend and we have been for a few years now she's a lesbian and she told me I'm cool with that and I never thought about going out with her but recently I want to be with her all the time and I want to kiss her and I want her to hold me and stuff like that...
she is more of the butch type lesbian and I'm really attracted to it and idk why...I've had 1 boyfriend before and its not that I didn't like boys, I do, but I also have a thing for my friend...help?!?!