The minutes on a Tracfone rollover and never expire as long as you keep active service (and for an extra 60 days even after you accidently deactivate.) You do NOT lose the minutes after 60 days.
You must however keep buying
airtime for your phone, like any other cellphone service. Unless you buy one of the 1 year package deals, you need to buy an airtime card ever 2 months, loaded with the appropriate minutes you want. Airtime is different from minutes. You will need both minutes AND airtime to talk on the phone. For your GM, I'd say the One year plan may actually be best as she won't have to worry or remember to add on minutes or airtime every 2 months.
The best way to utilize that deal is getting a referral to activate the phone for a bonus free 120 minutes (in addition to the minutes you get with the 1 year card.)
PLUS: add on a bonus code for the 1 year card, in which you will get even
more free minutes. (I think there is a 250 free minute code out now.) This brings down the price incredibly & loads up the phone with plenty of minutes, right from the start.
I can send a referral and detailed directions to get you set up.

Just send me a Private Message.
If she does want to add on more minutes, there are ALWAYS bonus minutes codes for free minutes to add on along with each Minutes Card - some are DOUBLE minute codes, so that cuts the price of a card down by half.
On the Tracfone website, there is a place to enter your zip code to see if they have coverage in your area.
Tracfone.com
Tracfone doesn't have their own cell service, per se. What they do is RENT cell service from existing carriers in your area. Instead of getting a Verizon cellphone, & only having serviced dedicated to Verizon, when I've traveled, the Tracfone SWITCHED to whatever carrier was available to me, in that area: Sprint, PacBell, BellSouth.
But check with other people in her area to see which companies get the best coverage. Some model Tracfones may be dedicated to those cell carriers.
Tracfone does give you 30 days to RETURN your phone if you find out, it doesn't have enough service/coverage for you or not the plan you want. I think this is what the "reconditioned" phones are. When you return a used phone, Tracfone has to wipe the old telephone number from it's memory before selling it again.
Also, many elderly carry phones on them instead of having those life alert alarms in case they fall. Saves lots of money. Even if they do not have active phone service, ANY cellphone that holds a charge & works is capable of calling 911, even if there is no cell phone service connected.
If she want's to carry the phone on her, make sure you get her a cell phone holder with a clip so she can clip it onto her waistband.