Grandparents are people who have had a houseful of kids for 20 to 40 years and are suddenly alone.
Of all people, we AS should understand what it is like to feel lonely and left out.
Yes, she is using the money as a bribe and a lever to wrest a visit from you. Perhaps she doesn't understand how much visiting stresses you. Perhaps (probably) she does understand this, but only at a logical level, without assciating the emotion to it. In either case, she is doing what grandparents do with and to grandchildren. It is not with malice, but out of love and lonliness.
Whether you go or not has to be your decision, based on whether you can take the added stress at this time. In either case, making a statement or writing a note to her, telling her that you love her, or admire her, or whatever, will help her and smooth thing over a lot.
This is from a grandparent (and greatgrandparent) who has been there, done that, received that.
Pops
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Tools are dangerous only while being controlled by a human.