www.cebm.net/covid-19/global-covid-19-case-fatality-rates/
Case Fatality Rate rate estimated to average 14.6% or be up to 16.7% for the over eighties age group.
“The majority of deaths are in the over eighties” does not mean “the majority of over eighties who catch Covid will die.”
If I were 90-something I’d much rather spend what, let’s face it, rather limited time I had left enjoying myself and taking my chances than hiding away and much as you might want your mum to live forever, the risk is hers to take if she wants to.