Have you considered medical marijuana? I live part of the year in California (where medical marijuana is legal), and while my personal view is that medical marijuana is overused (there are 'pot doctors' here whose whole practice is writing people scripts for marijuana for a fee - most of these people are not sick, but just enjoy the recreational effects. Not that there's necessarily anything wrong with that), it does seem to work VERY well for cachexia, anorexia, nausea, weight loss, etc.
I've known several people who had cachexia from AIDS for whom marijuana seemed to work miracles.
It's obviously not legal everywhere, but it's worth considering (personally, I would break the law to ease a relative's suffering, but that's just me...)