“Any time there are people present for whom there is not a problem of Yichud, there is no problem for anyone else who is there. ”
That’s what I thought, although I wasn’t 100% sure. Also, one case in which I don’t know whether or not that rule applies and I’m not sure what the halacha is: If there is 1 man, 1 married woman whose husband is in town, and 1 single girl.
It’s not a problem for the married woman since her husband is in town (assuming all necessary conditions for this rule to apply are in place), but would that make it okay for the single girl? בעלה בעיר doesn’t help her, so why should it be okay just because it’s okay for the other lady?