They now have meters, much like a blood glucose meter, that can test the blood for coagulation. My DH's doctor had approved it 8 years ago but he ended up off the blood thinners anyway, so didn't need it.
When they first came out, he wouldn't approve it, but later said they had worked the bugs out and it was more reliable. It would certainly make life easier for those needing this.
You might check with her doctor and see if he would approve it.
https://www.redorbit.com/news/health/1314037/medicare_to_now_cover_inr_self_testing_for_patients_on/TestingDale