thank you all!
misterartois - thanks for the 'advice'. the reason i don't put her down is because apart from being sick once every other day/36hrs - she is in remission and for all intents and purposes well. it would be unethical to put her down and i don't think any vet in this country would do that to her right now as they do not put down animals that are not sick (unless they are homeless or vicious).
she is not in pain, she is not 'ill', she is not even nauseous (nauseous cats don't eat or interact with 'life'). the reason she is sick is because cheamotherapy damages the tissue where tumours lurk, in her case this was her stomach wall, hence the reason why she is sick sometimes is because her stomach has become a little sensitive - it is developing some scar tissue from the cheamo and this can also affect the motility of the food (speed at which it goes through her). she is not sick due to feeling nauseous, it is more of a gut reflex - the fact she returns to her food bowl immediately after being sick is a sure indication that she is not feeling unwell.
believe me, if for one moment I thought she was in pain or her quality of life was compromised or absent, I would do the right thing - I am a responsible pet owner and have the guidance of an excellent vet. i really don't think death is the answer yet. but cheers anyway!