Turns out that lead was a dead end. My uncle just returned from that gas station and said the woman in the footage was someone else. However, we have recently hired a private investigator so hopefully some new leads will turn up soon, I'll report here if any do.
To answer your question, though, she does take a lot of medications. I'd say that she takes anywhere from 15-20 different meds every day. Her main ailments are, to my knowledge, liver disease, kidney disease, and type-2 diabetes. However, I think that these are unrelated to the reason why she disappeared in the first place. Lately, she has been under a tremendous amount of stress from several different sources. So much, in fact, that it literally caused her to have a vein occlusion in her left eye, which is similar to having a stroke in your eye instead of your brain. That was a while ago, however, and she seemed to recover quite well. Recently, though, her job has been very inconsistent and rather non-transparent about when and how they would pay her. At times, it was unclear whether or not she would get paid in the next month, or in the next 6 months. And I believe, from what my grandfather told me, that her job had sent her an email the morning that she left to run these errands that had caused her a great deal of frustration. There is no doubt in my mind that she either left on purpose with no intention of "running errands," or that she actually did go to run errands, and then suffered some sort of mental breakdown while she was out.