Lilmod,
This is where I said it myself (not sure who said it first but it doesn’t matter) I actually said it in reply to you!
Rav Frand also added that Rav Dovid (I’m not sure who that is, but the guys present probably know) would tell bochurim when they were dating to hold open the door for the girl even though this would entail walking behind her. (although personally, I don’t see why this has to be the case. Why can’t she walk through the doorway and then move to the side?, but in any case, that seemed to be his assumption)
Or why can’t he go first and hold it open for her