I'm have the worst, and best, of luck playing Man.

[Jack_Trowell]

Having Growth 1 should slightly lessent the chance to get a disease in late winter.
Having regeneration from a ring or blessing would prevent the crone from losing HP because of a disease, but it wouldn't prevent her from getting more afflictions from the disease or old age.

My advise would be to forge a thristle mace for the crone in order to increase its Nature magic level, as Nature levels increase the old age cap and enough of it might make your crone young again. It wouldn't remove afflictions, but the crone would not gain new ones anymore during winter.

If a thristle mace is not enough, you could maybe empower the crone in Nature. It is usually too costly to be worth the gems, but is you don't have already A4 with your pretender, keepeing the crone alive would allow you to build the Air boosters later (both need A4).