I saw your original post and jumped on here to discover that Kevin and Jill have already provided you with great advice.
My first thought was that a single mom, raising a disabled daughter is going to be a force to be reckoned with on some level. All mom’s are lionesses when it comes to protecting their cubs, but I would think the mother of a disabled child would be even more so.
I have to refer back to Debra Dixon (GMC). Any trope can work if you give the character the right motivation. Even those ones we think of as t00-stupid-to-live.