You should absolutely have an honest conversation with her about her finances and talk to both of them about at least informing you about any changes they wish

You should absolutely have an honest conversation with her about her finances and talk to both of them about at least informing you about any changes they wish to make before they make them. Old people are very impressionable, and there are some very shitty people out there who give bad advice. They also scare easily, so they might take all their money out of their accounts when the market starts to go down even a little. Apologies, no harm intended towards older people, just have seen a lot of them get screwed over. e.g. my managers Mom had all her (late) husbands retirement money in a pretty great account which was sponsored by her husbands company. But her friend convinced her to take it all out and hold it in cash, which turned out to be really really bad advice.