It doesn't matter in a legal sense, no. I think you may be missing a larger picture. Even if you find the nature of their relationship questionable, that doesn't mean a manager isn't free to take issue with you calling a co-worker a "bitch" in whatever setting. You're free to take up with the manager this person's behavior and work ethic as it relates to morale, and free to take it up with someone above this manager's head because you believe this worker's problems are overlooked because of their personal relationship whatever it may be. I'd stay far, far away from any mention of you thinking it's just her being treated better 'cause she's also Hispanic.