I would buy her some new short shank feet or whatever style it takes; they are going to be either short or slant shank. You could get her the basics or a complete set from Ebay for around 100.00. MIL's are a touchy subject. You don't want to come off as a meddlesome MIL to your Son in Law.
When the machine poops out you can both go shopping and perhaps invite her MIL along to share in the fun of machine shopping.