Hello Dragonfly. Sorry to hear that you are feeling so unwell.
I can relate to your being upset and triggered by your sis-in-laws rude behaviour and her cheapness. I have an almost uncontrolled desire to choke someone when I see them wasting life being overally cheap. I'm forced to be cheap by circumstance. but if I had money I would spend my time doing things that I enjoy and not trying to save a few bucks by trying to get the absolute best deal. I really hate it when a certain large corporation screws up my phone bill and I'm forced to spend an hr or two on the phone trying to get 20 or 30 bucks back, but it's something that I have to do. Once again, if I had money I would have better things to do with my time.
Having said that, once I get over my desire to choke someone, I feel sorry for them. They do have an illness, but they refuse to seek treatment and thus miss out on some of life's finer moments.
I hope that you feel better soon. Take Care. paul m