Also, her absence would have been conspicuous. Less so, now that we know what she does in the Galaxy and we may not need to see her again.
I think with her as Kylo’s mother she’s going to have to be around in the next two (or one if they kill her, but with Han dead already I expect Disney will ease up on killing old characters; I don’t think anyone wants “seeing your childhood heroes meet violent deaths one by one” to become a major theme of the sequel trilogy). Personally, I didn’t feel strongly one way or the other about Carrie’s performance. She was more than a little stiff, but she certainly didn’t ruin anything for me.