It depends when this was written! If it was written a few years ago, and she was diagnosed with AIDS when he was a small child, then that was in the 90s before the meds we have today became so readily available. But in that case I dont know if it would actually be more surprising that she made it this long once it had already progressed from HIV to AIDS but maybe its just the translation not being specific

Lol this is set in recent times right? AIDS is completely treatable if caught on time. And non-transmissible. So if she had no symptoms at that time meds would have completely prevented progression of disease and even cure symptoms she did have. Doesn't make sense for her to die unless she didn't have medication.