My parents are both 92. This week my mom's blood pressure has been 180/110. She refused to go to the hospital or a temporary stay in assisted living. she and dad live in an apartment at a senior center. my dad went into assisted living, supposedly temporarily, a few weeks ago. the staff doesn't think mom is well enough to take dad back into the apartment with her but she keeps saying she is. she has aged terribly these last years taking care of him. and she is really, really stubborn. i'm an only child and it is hard to know what to do.
I woild be worried about the danger of stroke with bp that jigh. Will she go to the doctor, to urgent care or the er to have that checked out? For me, with my mom, sometimes it was a matter of telling, not a sking. If i asked my mother if she wanted to get something checked out, she'd say not. But if i say "qe're going to the X doctor, she's pretty agreeable.
You might just have to wait until there is something really serious that happens before your Mom or your Dad will realize they need another layer of help... [sigh]
It becomes a waiting game, and wait, and wait.
I also agree with Babalou, that when our folks get older and their judgment is going, you have to step in and assume the "parental" role and just tell them you're doing X, Y, or Z. Tell her you love her and you're concerned for her and you won't rest until you know she's doing OK.
Pull out all of the stops and try everything to see what works. Then remember that trick for future use! You gotta do what you gotta do.