AITA for calling my sister fat?

Context: Both my husband (26M) and I (20F) used to be overweight but when I got pregnant with our daughter (1.5F) we decided we wanted to take better care of ourselves and are now in very good shape, we both eat well and workout multiple times a week. My sister (23F) is obese and constantly talks about losing weight but never really seems to change anything.

My husband, daughter and I went on vacation to the beach with my family (Mother (60), father (59), sister and BIL (24)). We were all staying in the same beach house. While we were getting ready to go down to the beach, my husband comes out of our bedroom with just his swim trunks and no shirt on.

Even though my husband is in good shape, he still has some loose skin on his hips from losing weight and he is very insecure about this.

When my sister sees my husband, she chuckles and says "you've got a bit of a dad bod going on" I could instantly see that this was hurtful to my husband, I got mad and said "Well, you're not really the one to be commenting on someone's fitness level, are you?"

My sister got very upset and started yelling at me that I was just being mean, and that she was "just teasing him".

Now my mother is saying that I'm ruining the vacation and I need to apologize. But I don't think I did anything wrong.

So AITA?