Lied about my age

First thing you should know is that I'm a woman and I'm straight (this is not a question regarding my sexuality). I was walking in the city yesterday and bumped into this amazing woman. I'd never been in the city before and wanted to know where to eat so I asked for her suggestion. She was very friendly and offered to take me to her favorite place and even pay. We walked to this awesome restaurant/bar and sat down at the bar. I talked to her for quite awhile before I ordered anything. Basically I thought she was so much fun to be around, super nice, had so many adventures, knew celebrities, blah blah blah. She asked me how old I was and the first thing that came to my mind was 22, which is a lie and I'm actually only 20. I regretted it as soon as I said it and I feel terrible about it. I had already been served an alcoholic beverage before she asked (I was not carded) and I lied for selfish reasons. I really connected with her but I'm afraid if I tell her that I lied about my age, she'll be pissed and tell me to f*** off basically. She was very blunt when a stranger interrupted our conversation, and I admired her for it, but I would not want to be the person that she's telling off (she also isn't from the states). But anyway, I'm turning 21 in five months. Thoughts besides that I'm a terrible/selfish person? Would should I do?