Is it normal to love having lesbian sex with you best friend?

Okay so I'm a girl and bisexual. I LOVE sex, I've had this friend since 4th grade and I dunno why but I LOVE having sex with her. We aren't dating, I don't think I ever would date her, but she knows how to pleasure me in a way no man has ever done before. Jeez just thinking about it is making me want her x_x
Is this normal?