Not sure exactly what qualities of the Jitterbug phone you/your neighbor most want. But generally speaking, for seniors-friendly phone service and devices, it would be worth checking out Consumer Cellular, including (but not only) the device they call the "grandpad."
They've been my phone company for several years and I've been very happy with them. Older people = their primary target market, but their plans are open to anyone. They seem to put a lot of effort into making things easy for non-tech-savvy people. I've found their help desk people communicate very clearly and patiently. I swear by 'em.
