DD is 14, she is a bit overweight for her height but we don't draw attention to this and prefer to focus on healthy habits, no/limited junk food, portion control, physical activity etc. DD is generally very happy, doesn't seem to get picked on at school etc.
DD is not my DHs child, we have two children together who are 8 and 10 years old. DH also has a son who is 26.
On Saturday we all traveled into London and met up with DSS and his gf, we went to winter wonderland, did some shopping, then went back to DSS's girlfriends and ordered food in. Lovely day for the most part. I noticed on the way back DD was quite quiet, thought she was just tired. Last night DD told me that DSS's GF said when they were looking at clothes together "you should try slim down, it's healthier". DSS's girlfriend isn't British. I told DH, who messaged his son to verify. His DS replied "I don't know if she said that but if she did she wouldn't have meant anything mean, she's just forthcoming, it's cultural".
DD was extremely upset and has said she doesn't want to spend Christmas with DSS's girlfriend, but we are meant to. I told DH this and he is in camp we can't uninvite her. DD has now said she will just go spend it with her dad then.
AIBU to say this was out of order and we should prioritise DD who is still a child feeling comfortable at Christmas over his adult DSS's GF?