I think you should leave it up to her who she would like to spend the holidays with. Since things are pretty new she might just not be ready for the big extended family thing anyway (especially if she hasn't been spending a lot of time with her own family over the years). I'd let it go for this year and maybe discuss the posibility of doing something special with her for new years.
Everything will be ok in the end. If it's not ok it's not the end.