I had a sim like this a couple of years back and was sure she was glitched. I asked how I could tell in the bug forum that was on these forums then but not now. Crinrict suggested that I try killing her by Cow Plant. If she was glitched she wouldn't die and if she wasn't that would take care of it, if I was ready to let her go.
I did a save as on the game first in case I felt guilty, if she died. Turned out she did die and I found I was relieved to have her finally pass on, lol. She's only the second sims I ever intentionally killed and I've played all the iterations of The Sims. The first one oddly enough was in TS2 by Cow Plant, too, but I felt guilty and had a controlled sim bribe Grim to resurrect her :)
