People often confuse the Medicare/Medicaid aspect of long-term care so don't hold that against the posters.
The Medicaid cutoff is around $2,800/month. Depending on her exact SS payment she might miss it but something to consider is which SS check is she on? Hers or a former spouse's check? I can't remember the rules on changing from one to the other but if she's on the bigger of the two checks, and it's possible to switch options X numbers of years later, AND you were desperate for financial assistance once the $210k runs out, then maybe inquire about swapping her to the lower of the two checks (if that's even an option), to qualify for the more-valuable-at-that-point Medicaid payment.
As it stands, with the SS and the $210k, she's got enough to carry her for a decade at conservative rates of return. Not to sound crass, but in her current health state, that's likely going to be long enough. Good on you for trying to plan ahead with all of this but you may just be in a "wait and see" window when it comes to what you'll need to do (if anything) a decade from now.