My aunt, who never married, is 94 and, in recent days, unable to care for herself. She is not frum. Saying that it is not dignified to live as she is, she wants to die. How shall I daven for her? Shall I ask that she have a quick, comfortable death? And what can I say to her?
You ask a very delicate question, for we all know the value and love of life in Judaism. On the other hand, we find several places in the gmara where students prayed that Hashem should put an end to the suffering of their teacher and they subsequently died, for example, Bava Metzia 84a, Ta'anit 3a. The Ran (Nedarim 40a) even opines that there is sometimes a mitzvah when visiting a sick person to pray that he should die and be redeemed from his terrible anguish. On the other hand, in Resp. Mishneh Halachot (8, 239) R. Menashe Klein suggests that they davened that G-d end the suffering however He sees fit, not necessarily to end life. R. Chaim David HaLevy (Resp. Aseh L'cha Rav 5, p. 398), allows to hasten death for one who is suffering where there is no medical hope for survival, if the patient is not a relative, and surely not a parent (where it would not be respectful to say such a thing). R. Eliezer Waldenberg (Hilchot Rofim uR'fuah, p. 204) explains similarly that the problem is that it may appear that relatives seem to want to "rid" themselves of the "burden" and responsibility of caring for the demanding patient, yet allows it if that is clearly not the case. In short, the best thing to do is daven that G-d end the suffering however He sees fit. Additionally, you should try and utilize the time with her to help in any way possible, through stressing what she does have to live for and/or distraction, humor, reminding her of pleasant memories, and strengthening her belief in the world-to–come. You may want to ask her if she would like you to say Shma Yisrael with her, as the saying goes: There are no atheists in the foxholes!". At times when doctors and medicine are of no help, many find it most useful to "Lift up (their) eyes to Heaven". With Prayer and Hope for all of the Sick of Israel, Rav Ari Shvat