When I've looked into the details before, I found that the Jitterbug service was overpriced. You should be able to get a prepaid phone for less monthly cost. My parents, who are about the same age as your aunt and don't text or use many voice minutes, have flip phones from Virgin Mobile.
Virgin Mobile | payLo Talk & Text Plans
Virgin Mobile uses the Sprint network.
You mentioned a preference for the Verizon network. There's prepaid service from Verizon, too.
Prepaid Phones & Prepaid Plans: Cell Phone Plans | Verizon Wireless
Look all the way down at the bottom of that page for "Pay As You Go - Talk and text on Basic Devices."