Maybe they're using "nurse" in a general sense, rather than meaning she's an R.N. She could have been a health aide of some kind; the fact that she couldn't pay for car repairs suggests she wasn't earning an R.N.'s pay.
"Nurse" probably refers to an LPN or nursing assistant..the kind of employee who often works at homes for the elderly. High demand but very low pay. Undoubtedly more lucrative to stay home and collect welfare while minding the young kids.
So her kids burned the house down while she was home, and it was her 13 yr old son who got everyone out. I wonder if she was even sober?
You are right, there's a big difference in pay for an R.N., L.P.N. and a Nurse's Aide or assistant. A difference because of the education levels among them.
An R.N. where I live commands decent pay and I suspect it is the same everywhere.