Replying to What should I do?

So on Friday night, I went to a deadmau5 concert at the congress theater in Chicago. It was an 18+ show but i'm only 16. My cousin gave me this kids id from USC so that I could get in. It worked but when I was in there, I met this girl and I was hooking up with her. She asked me how old I was and since I was drunk as hell I told her I was a freshman at USC. We exchanged numbers and texted for the rest of the weekend. Shes a senior at a highschool about 45 minutes away from my house. Now she wants the d and I dont know what to do. Should I just keep going with the freshman in college thing, or tell her the truth, or admit that im in highschool but lie and say im a senior.