Are you interested in getting back together with her?
If you are, be careful. If she isn't interested and just wants to have sex, it's hard to not get emotionally involved in a bad way. Thus complications.
If you don't want to get back together, be honest about it and you shouldn't get into too much trouble. I had a ex that I had to constantly remind "I'm not going to be your boyfriend again. If you're not alright with that we need to stop doing this." It kept expectations realistic for both of us.
That having been said, I am wont to say GO FOR IT! Consequences?? pffftt...
also, wear a condom
If you are, be careful. If she isn't interested and just wants to have sex, it's hard to not get emotionally involved in a bad way. Thus complications.
If you don't want to get back together, be honest about it and you shouldn't get into too much trouble. I had a ex that I had to constantly remind "I'm not going to be your boyfriend again. If you're not alright with that we need to stop doing this." It kept expectations realistic for both of us.
That having been said, I am wont to say GO FOR IT! Consequences?? pffftt...

also, wear a condom