There is no age boundary for putting artificial teeth. Taste may reduce, but function, digestion and nutrition are very important in elderly. I would request you to go and get her artificial denture preferably by a prosthodontist. I must tell you that most of the prosthodontists have experience in making dentures for 90 and 95 year olds. Please do not leave her. If you will not get her dentures, she will suffer badly.