While slightly more clearheaded, I have checked the days my mother Sim had left on the first day until Adult, and her current days remaining until she's an Elder, against the current game week and day, and her age is correct - it hasn't been reset by anything. That was the flu freaking out amidst the realization I'd done something I'd made a note not to do.
I really thought it was over. I will wait to proceed any further until I'm very sure that the 1500-Simoleon Volcanic Clay Bath option at the Spa is not included in the ban list under "mud baths". Apparently it didn't actually do anything to her age--it just really sounds like a "mud bath" to me.