Platitudes spoken after the death of elderly friend have a way of turning into justifications for that death. This is the flip side of the "fair innings" argument that is used fairly openly these days in rationed medical systems to direct resources away from providing treatments to the old. You have lived, now get along and die. Or perhaps it is a little of the old evolved conservatism in human nature, the urge to conformity: everyone else is dying, why not you? Or perhaps this is entwined with ageism, that older people are worth some fraction of a younger individual for whatever justification makes the everyone feel better about themselves. Even the older people go along with this, which is a shame. A death at any age is just as much a loss, and in this era of nascent rejuvenation biotechnology, members of the research and development community could be achieving far more than is currently the case to improve health and reduce mortality in old age.
You're probably familiar with the feeling of slight disappointment that you may have when a good thing - say, a nice trip - is over. Just as you say that it's too bad that the experience is already finished, someone will probably say that you had a good time nonetheless; an innocent, fitting expression to cheer you up a little bit. This phrase can be harmlessly used in a variety of circumstances, but there's one in which it really doesn't fit at all, yet people keep using it: when somebody dies of aging.
Death always has a profound impact on us all, and there's little or nothing that you can say to cheer up people who are losing their loved ones. Yet, we all feel that we must attempt to relieve their pain, and this kind of cliché has been repeated over and over for millennia; it's hard to give up on using it, as it's the only weapon, however ineffective, that we can use to sugarcoat the bitter notion that what happened will happen, in some form, to all of us. What I object against is how these set phrases are often used as more than mere uplifters; they become justifications for death. Just like people say "well, you had a good time" when your holiday is over, they say "well, she had a good life" when somebody dies, as if this made it any better; as a matter of fact, these two situations aren't even similar.
As a side note, you wouldn't say "well, he had a good life" in the case of someone who is dying before old age. You would say "oh, but he's so young!" Apparently, if a young person is dying, whether or not that person has had a good life thus far doesn't seem to make much of a difference. This betrays unintentional age-based discrimination: if you die young, that's a tragedy; if you die old, it's not so bad as it would have been had you died young. This double standard is fueled by the misconception that an old person wouldn't have much life left anyway, so it's not much of a loss if he or she dies. However, the remaining life of old people isn't short because they're old - it's short because they're not healthy enough to live a long time, and we aren't yet capable of fixing this.
"Well, she had a good life" is part of a plethora of other set phrases and coping mechanisms that, historically, have allowed humans to come to terms with mortality and allow the species to go on. However, they're just a hindrance now. It's true that rejuvenation is not here yet, and we're very far from being able to promise anyone that they will never die. However, rejuvenation science is in its infancy, and mindlessly perpetuating these coping mechanisms will only serve to delay its transition into adulthood. As we keep striving to bring aging to its knees, the time has perhaps come to find new, more rational ways to cope with the inevitable losses that will happen until that moment comes.