Going from memory, I think I've seen people mention before that they've transferred their Safelink service from one TracFone to another. I'm sure someone will chime in with first hand experience.
I highly recommend the LG 220c. It gets stellar reception, sound quality is excellent, and the battery seems to last forever. The newer CDMA LG flip phones aren't as robust.
I think going with a CDMA TracFone is a good idea if it will work in her house. I have good coverage from both AT&T on GSM and Verizon on CDMA, but I always seem to end up with some garbled voices on my AT&T TracFone. I much prefer my Verizon TracFone.
Castrol EDGE 5W-30 is my drug of choice.
Primary: iPhone 6s Plus 64GB, Galaxy Note 5, LG G5: 5 lines, 3x $5 Android web, 1x $2.99 T-Zones
Secondary: TracFones: iPhone 5s [AT&T] & iPhone 6 [Verizon]
Mobile Broadband: ZTE Z915 LTE hotspot (5GB for $10) + iPad Mini Retina w/ T-Mobile LTE