Where do you find common ground with your teenage daughter?

Just recently my 15 year old daughter did something to get into hot water She ended up grounded for 30 days (I think she got off easy). She is grounded from her cell phone, the intranet, staying nights out with anyone and talking to boys. She constantly tries to lay on the massive guilt trips about letting her talk on the phone to one boy in particular and we keep saying no. She says you don't understand this guy is different. I just told her firmly and politely that she should have thought about that before she did what she did to get grounded in the first place and that she has no one to blame but herself. I feel I am doing what I think is right on teaching her that some rules are not meant to be bent or broken, especially one as important as the one she broke majorly.