So I booked a restaurant for my girlfriend's birthday three months in advance; it was a restaurant she really wanted to try, but they are always booked, I told her in advance I wanted to spend the night with her but didn’t specify the restaurant because I thought it would be good surprise. A week before her birthday, she tells me she just wants to go out with her friends and not sit in a restaurant but she wanted to spend the day with me.
I took her go carting on her birthday and on a picnic because she had been telling me that she wanted to go on an aesethic picnic, so I made sure to prepare everything with the ambience she likes. I didn't get her a gift because we are both financially secure, and if she wants something, she will not hesitate to buy it.
She hangs out with her friends, while I hang out with my sister, which she is well aware of. My sister and I have a good time, and when I get home, I go on my phone, and when she arrives, she is upset because I went to the restaurant (she apparently saw it on my sister snapchat). She said she wished we could have done this together and that she wished I hadn't gone because she had been wanting to go and that I should have given her the reservation as a gift since I didn't get her a real gift and her friends could have done this together. I was able to change the reservation from two to three seats, but I doubt she could have changed it to eight seats.
Anyway, she slept in the living room and has been guilt-tripping me. At this point, I'm irritated and don't feel like apologizing. I'm not sure if I did anything wrong. I sort of think she is overreacting, in my opinion, but I don't know. Maybe an outside perspective can make me understand why she so upset.