50, divorced, and special needs kid?  While much or all of that is no fault of her own, I can't help but wonder what world we live in. For her to retire would be like someone who's 35 and childless, not divorced, tagging out, declaring themselves to have worked enough after their arduous 10 years on the workforce. 

Life is like, 90 years long. If you're only contributing (economically) to society for 20 or 30  years out of that, then who is creating the wealth on which you live?  Oh yeah, everyone else.