Is it normal i had sex with my best friend!?

Ok so i ended up becoming friends with my neighbor who I thought was fucking sexy before I even met her. we started drinking on the weekends and hanging out I felt a strong attraction to her from day one, I also felt an attraction from her. We are both very freaky girls! we got to know eachother and became better friends. then we got drunk one night and fooled around.. It has happend multiple times now and we are best friends, is it normal for friends to do this or do you think it could be something more serious than either of us are realizing...