Try a different approach. The next time she wants to buy you or the kids something - tell her that you would just prefer a donation in your name to a favorite charity. Perhaps a Humane Society or rescue group, a church, a mental health facility!!! If she does actually buy something and dump it on you, then just tell her you are going to auction it on eBay and donate the money to a charity. That way you aren't refusing anything and don't have to feel guilty or responsible for any of her actions.