I think my dad's former partner tried to do this. He later found that she was slowly stealing his money, but when they were together he ended up being diagnosed with MS. Since they have separated, his MS has stopped progressing, though he still suffers constant chronic pain his condition has not progressed. He still works full time running a large farm, in his late 70s. Women poisoning their partners is not as uncommon as people think, it's probably one of the more common methods of violence committed by women, as it does not require physical strength.