Missing events

I have a one year old son and also another baby on the way. Ever since I’ve had my son obviously things have changed. We don’t get to go to as many birthday events, parties, and things like this. I’m a younger mom so most of my friends are still in their “party days”. I’m only 22, but I’ve been so done and over the partying for a while and so has my husband. I have a friend that constantly plans things around 7:30-8 at night (which isn’t a problem for them), but 8 is when my son goes to bed. I don’t mind missing these events because I absolutely LOVE spending time with my son. My problem is, this friend, always seems to get upset when we don’t make it. I’ve told her time and time again that we can’t make events that late due to us having a child now. She doesn’t seem to understand having a child changes everything and you can’t always drop everything and do what you want no matter how far in advanced you’ve had it planned. She makes me feel guilty some times for not being able to make it. I don’t really see her much because she’s one of those people I can only take in very small doses. I don’t want to be rude, but I honestly have more important priorities in my life. Am I wrong for this?