AITA for making a big deal over my free birthday dessert?

I was at a casual dining restaurant with my mom and sister for my birthday. When the server asked if there was anything else we needed, I said "I think we're good. But, it is my birthday. Do you guys do free desserts or anything?" The server said, "Yes! What kind would you like?" And I picked one. She brought it out at the end with a candle in it, and my mom and sister sang and I blew it out. <br><br>My girlfriend heard about this through a mutual friend and was angry that I didn't tell her, herself, because she wanted to do something with me for my birthday. So I asked her what she would have gotten me for my birthday, and she said she would have sung and given me a cake with a candle. I told her that's what I did with my mom and sister. <br><br>My girlfriend said it wasn't the same and I deceived her and lied to her by not telling her I had already celebrated my birthday like that. I said, "I went out for dinner and got dessert, c'mon." She says it's a big deal and I feel like it's not. I don't even remember her asking me what I wanted to do for my birthday.