@Rogar It's possible that he actually doesn't know. Though odds are that he does, this other woman could be the woman he intends to "make" our female lead into in order to pacify family and rumor mills. It's possible Albert is "gay" for our girl and wants to cover it up with a believable scam. Like in that one story about the two cross-dressing dudes who fell in love with each other's female personas.
@UntappedChaos if the conversation had come up anywhere else it's possible that it could have been cleared right away too. bummer. On the other hand, the description did say our girl is gonna be invited to be Sir Albert's dress-wearing partner, and from the description, it didn't seem like that was gonna be a late-game development. So it's likely that the "other woman" misunderstanding will be cleared up quick. I'd say two chapters of confusion, maybe three.