She has been an experimental pin cushion in her home state of Washington, and along with her MS which has destroyed her life, she has had some pretty life-challenging heart issues too.
She's only in her mid-40s but she doesn't have many years left, as my sister tells us.
With her heart issues I think she can best decide with her personal doctors if she should get it.
She has chosen not to be vaccinated for now and why can't the government and vaccine Nazis and yes even the "MS society" just say OK - and respect her decision. Her Body, Her Life, Her Choice. They can assess the risks pro or con.
And I think the statement from the MS Society link you posted tells us enough:
"While research is underway to learn more about the specific experience of people with MS receiving a COVID-19 vaccination, data on the safety and effectiveness of COVID-19 vaccines in those with MS are limited. Our guidance is based on clinical trials of the general population and studies of other vaccines administered to people with MS. Our guidance will be updated as more is learned from scientific studies of the vaccines."
Not every one is 'the general population', and if you could see how her life has changed since she first acquired MS I think you would agree not all feet fit the same shoes.