Does doing this make me a bad friend?

There is this guy we will call bob. And he is kinda one of the really popular guys at school and hes like the best all around guy. Last year i started to talk to him a lot and kinda had a crush for awhile and then it went away. This year we picked it up again and have been flirting and playing around a lot. He dated a girl i knew for 8 months and they just ended. The day that they were over for like the 7th time [they broke up so much] he texted me and said im single and free to flirt so you are first. we had a lot of dirty texts back and forth and then we started talking more and more and flirting for a couple days. Im really starting to like him but my friend, tasha has liked him for a really long time. He has no interest in her at all and has a lot in me. If flirting with him making me a bad friend to tasha?