It's not bad-mouthing others, but rather simply FYI for your boss. Besides, you will have both the person you are helping and your boss in the email.
Look, if you feel that you are not part of them, be it them or yourself, how good they perceived you is not important. As long as you are fair, to yourself and others, you can work together as a team. You are not there to make friends, just do your job.