So you talked to a shop worker about your w spending habits? That is just so strange - and stalker like! Currently you are no longer together so can she not spend money on what she wishes?
As for Christmas dinner - enjoy the time with your kids. What positive would come from inviting her over? Your last conversation seemed to be about making your wife apologise.
M: 17 T:17 Me:42 H:48 BD 23/12/2017 H says ‘I don’t want to be married’ D 17 D 15, D 13, S 10, S 10