What obligation do I have to this woman?

Go and pay her a short visit say maybe a half hour.Maybe she can not help the way she is because she is in pain or frightened about being a lone and her ill health.Bring her some flowers,they need not be expensive just some from the grocery store will be fine.If in that half hour she gets to acting up just smile wish her well and go.Then you did your part and you need not go back.

She was somebody's little girl once, and somebody held her in their arms, and at some point along the way, she fell out of step with time and people and things, and as time as gone by she has become embittered and maybe a little insensitive and such, but that's because she's never had anybody like her for just who she is, or just want to sit and listen to her side of life's story, she's a person, and has a whole history, and think about what that would be like to be her, to be inside her head.

I'm sure your presence (whether or not she shows any appreciation or not for it, or is rude to you) is a good thing in this universe from an outside perspective of either of you.

Do it, and just do it because no person should have to go through life utterly alone or forgotten, at least one afternoon is something.

She may have undergone an epiphany about her behavior, in any case, she is in a horrible place with no one who cares about her so I think you should go as a kind gesture. She may or may not be rude but it will be good for your soul...and hers.

Stop showing off and actually do something lady.

humanity