On the other hand, if she will not let you out of the Xmas with her family, don't say anything about them not treating you well. Instead say that you don't feel comfortable there. And ask her to speak to them about trying to make you feel comfortable so you won't want to go to Xmas at your family's. Be careful not to insult them. You just feel out of place there, maybe they could make you feel more welcome. That is not accusatory. That is talking about your needs. A different thing entirely.
