Autumn rose
Given her advanced age, I think the most realistic replies are the ones that frame their advice in the context of her advanced age...since you said you want advice on ways to help her, Rather than just quick advice on how to oust her, I would
** ask if she's willing to see a doctor to be screened for any possible underlying issue that is age related, such as depression, early stage of Alzheimer's etc etc and then address those if any apply
** frame whatever help you provide within the context of her age, make sure its relevant to her age. If she was 48 it would be reasonable to simply get her into apartment. At 78, that is a whole other thing. She is in need of something beyond just a pad to live. Sme others here have addressed this really well....even if she seems healthy now, things can change fast at that age. If your dead set against her continuing to live out the remainder of her years with you, The recommendations to help her fnd senior housing is excellent advice. I know someone who's parents run a senior agency, they are advocate for seniors well being and protection, and have tons of info and resources on housing, healthcare, end of life issues, etc. others recommended getting the help of one of these elder care agencies as you navigate your way in the process
This will help avoid a disaster of making some quick plan that fails later bc it was not relevant to her old age