What do I do with my girlfriend that forces me to go to bed when she does?

Let me preface these comments with the fact that I am both a full time student and full time public relations account coordinator. My work often forces me to take projects home with me. So by the time I get everything done my only free time ends up being late at night. So my problem is that my girlfriend freaks out that I am still up when she wants to go to bed (Even if we have already had sex that day). I try to tell her just to go to sleep but she literally bitches at me and tells me I am ruining her health because I stay up late and in doing so, keep her up. This honestly seems crazy to me because I could go to sleep if she was up writing or watching TV. I just want to relax, read some news and write but am forced to fight with her about this bullshit until I give in and go to bed. We've been dating for a year and a half and she only recently moved in to my house. Most of the time, she is amazing but I cannot stand the way she freaks out on me about this. I keep asking myself, "is this going to get even worse if we ever get married." I seriously value this time. It's the time that i get caught up on everything. I don't know what to do. I've tried taking and she just calls me crazy and says no normal person would ever put up with this.