Although interestingly Kitty owes Magneto for being back on Earth and removing her from the nutrabullet she was in. Kitty holds grudges. Period.
I agree that Rachel has a completely different relationship with Magneto than Kitty, especially because of her relationship with 811 Magneto and that they both lived in concentration camps. Over the years Rachel has waivered in her support for him, especially when he was back to his 'villainous' ways during the X-Men reload era which she was in London for and surely heard about. And she knows that Xorneto wasn't Magneto and that it was Sublime who killed Jean, so there's no confusing that issue. I think that Rachel, like others, have given him the benefit of the doubt multiple times only to get burned in the end. For Rachel recently, while she sided with Magneto during Civil War II to help save the mutant race she was really upset about Magneto did while she was holding off the Inhumans and all of Attilan. So much so she left him right afterwards showing her distrust and displeasure. So it makes sense to me that if you recently had a terrible experience working with someone and trusting them, you would in fact not be supportive of others doing the same. Right?Rachel its a bit more sketchy. She came from a world where Magneto was the hope and inspiration to mutants because the world was an utter nightmare for mutants and she missed out on Magneto building Asteroid M and going on his mutant messiah kick in the 1990s as Gold 14 talked about.
But, she has had moments the past decade where she vacillated between working with Magneto and completely distrusting him so its not against continuity. I would say the easiest mental rationalization for it is she is confused and conflicted about the Xorneto killing mom stuff. As in the past she sends a SOS message to Earth and doesn't trust that he isn't there to save her?