Remote access to Mac that cannot update TeamViewer

I'm not sure if this is the right board to ask this question. I use TeamViewer to support my 94-year-old mother-in-law who uses a Mac vintage 2010. Today I got the message that she needed to update her version of TeamViewer in order for me to connect to it and solve her problem. However, her version is the latest one that is supported on her OS and OS is the latest one that her hardware supports. I only need to help her every month or so, and this is the only connection I use with TeamViewer, How can I solve this problem? Thanks for your help.