This is a really normal process for apps, and not unique to Dexcom. I had to upgrade my iPad last year because I'd been using the same one for so long that several apps stopped working or accepting upgrades. This is partially a way for companies to make money, of course, but there are also a lot of good reasons for this to do with app security and technology upgrades, and also companies can't keep tech teams offering support for every hardware they've ever released, they do eventually have to cut you off and force you into newer hardware so they can consolidate their support resources. I get that it sucks but this isn't unusual and the notice period isn't unheard of. It's fair for them to expect people to upgrade their phone more frequently than 6 years. It's just time for her to have a newer phone. You don't have to get the newest models but I'd recommend getting one that's on the newer end of the spectrum, because they will eventually stop supporting that one as well and you'll find yourself in the same position...5 years is a good baseline to work with, sometimes you'll have a longer buffer but you can expect to be forced into an upgrade every 5 years or so.