Hi Dee,
It's obviously painful for you to think of sis-in-law's last few years, but sounds like she did what she wanted to do. Some people are content to keep a low profile and rarely go out; I suppose it's a coping mechanism mixed with the practicality of actually planning a trip out. But don't beat yourself up over the last few years! You're there for her now, that's what counts.
So many of us have had really close friends fall out of contact with us. The fact that you write to her and make the long trip to see her, massage her hands and tell her you love her is truly heartwarming.
Whatever happens, happens; much of it is up to her. She is lucky to have you.
Love Ellie.