I need advice.

I'm seventeen turing eighteen in October. So i have a single needy parent. She always expects me to be home. The only time i go away is for the weekend to see my boyfriend. I ask to go away just for one night on the week to see my best friend which i never see anymore. She tells me no, pretty much for no reason. The family/siblings rarely bother with her. Just me & my mother live together. I asked to go away for one night & now she's telling me if I leave i have to stay there for a week? She is bipolar so I'm not sure if that has anything to do with it. She just treats me more like a friend then a daughter. I don't know how much more i can take. I feel like i have no life & i only have one friend. I think she's being selfish because she always wants me around to keep her company...I'm just trying to have fun for once. Should i go see my friend?