@kcw4smwdc . . . suggestions for guilt vibes coming from spouse . . .
As you know, life is unfair in the responsibilities and tragedies trust upon us. In a well balanced world, we all take our turns to carry the burden: my husband cared for his mother and aunt, my sisters were main care for our mother but neither of them helped with their spouses parents, I am caregiver to our younger disabled sister. I have to say, none of this happened without some resentments and guilt shaming all around.

I empathize with you for the situation you are in. And I feel, and have felt, the feelings you mentioned.

Would it bring some relief to you, and your spouse, if you just tell her you agree with her?
Because you probably do -even though you don’t have a choice in the needs your parents have and who is going to provide that.
It is a lot! It takes your time, which it would be so nice to be able to have the freedom to choose what you want to do with it instead of more responsibilities.
Being “dumped on” is an unfortunate choice of words with an implication that the dumped on person isn’t strong enough to push back. But I don’t see it that way. When someone uses “dumped on” my guess is that person is afraid, powerless, scared -because they don’t see the strength it takes to do the right thing. They see things as if the person who pushes hardest gets what they want (and yes that is too often true). But not all of us can be pushed.

I did get frustrated with the time and emotional toil it took when my husband provided are for his aunt. But I married him because I needed and wanted the exact type man who would take on caring for others.

You’ll probably get other, better suggestions than mine, but maybe just saying, yes, you’re right! This is an unbalanced unfair burden! It might take the fight out of the words.
It takes strength, not weakness, to do what you’re doing. It really is the ebb and flow of human life that these responsibilities come and go.