You could just be rude & tell her that you have heard this over & over again & it's obvious that after this much time she has no interest in doing anything but complaining about her life so you would appreciate it if she would just keep her whining to herself.

Retire.

Find a new job

& of course there is always the ignore method.

Really, not to make light of your situation. I understand how hard it is to be around this. There is probably no really good solution & I am sorry you are having to work around this negative situation