I say get her ZTE AVID.
yes its true ZTE isnt best brand, its not even close but since its for your mom I don't think she needs the best phone out there. The specs are decent.
There isn't root for it and that would be a deal breaker for most of us but I doubt it is for your mom. I think the AVID will fit all her needs
or you can try getting a good deal on a used esteem.