Should I tell her, or not?

I've been going out with (A) for 2 months now and since day 1, we had connected more than we had ever connected with anyone else before. Beforehand i had a really good friend (B) who is a girl. Once i started going out with A, she saw B as a threat and asked for me to stop hanging out with B alone and if possible, stop talking to her because she knew B had a thing for me and i used to have a thing for B. I complied and we went on. After a while i went back and started talking to B again. The on and off with the talking went on for a month. A found out once, we argued, fixed things, and went on again. *Quick info: i used to smoke weed frequently and stopped due to my being arrested back in september. Hadn't smoked since until recently* B got me back to smoking weed. "A" doesn't like the whole party scene, aka smoking/drinking/ etc; I hid the talking and definitely the smoking with B from A. Have been keeping it well hidden. But progressively through the ordeals i find myself getting closer to A but a little closer to B. But my mind is clear now and i know i find myself more attracted to A in every aspect. But, when B and i had smoked together, we afterwards made out or hooked up (just fingering). Both only happened once. I don't know whether or not i should tell A and risk a breakup and losing her or keep everything hush hush and never bring it up. Any kind of response appreciated.

Don't tell A what happened. What you did was wrong yes, but it was a mistake and its in the past, don't bring it up now. Focus on making your relationship with A stronger. I think you made the right decision for not leaving her for B, I feel like B would have just brought you down again.