"she can't be trusted' - your own words. It would serve nothing to try to get on her good side then. Move on and rest easy you are making the right choice.

Beyond tacky? I couldn't have said it better myself. Who asks for gifts for a repeated exchange of vows anyway. The whole point of gift giving is to set up a happy couple with things they will need to forge a life together. I imagine a couple that has been together for 30+ years already has everything they need in their existing household. Yeah, this is gauche - humorous even. Does this not have an air of gimmee gimmee?

No, no need for a gift. What would I do? I would observe the occasion with a simple card indicating congratulations.