DP and his DD (10) had been invited round for Xmas dinner on Xmas Eve. DP and I do not live together. My DDx2 (5yrs, twins) are off to their dad's on Xmas day, so we're having a pre xmas xmas on Saturday. I sort out cooking, pressies etc as if it was Xmas day. DDx2 adore SD. SD an only child. SD decides suddenly she wants to do "something else" and has announced via DP she's going shopping instead with her friends. DDx2 devastated. I'm annoyed with DP for not standing up to her and explaining better the significance of the day and encouraging her to come along. AIBU?