I'd love to get my mum using something FLOSS and secure like Jami, Jitsi etc... but that could be bad for the people she's communicating with. They're in China (the ones she's talking to in WeChat) and Hong Kong (where WhatsApp is still OK... for now).
Just having something like Jami on their phone (or Jitsi in their browser history) could get people into trouble there. And she doesn't want that, nor do I.