In the immortal words of Queen Amadala, "You assume too much."

We arrive in the scene with the girl looking at her phone and the couple making a statement about the girl. We don't know what happened before. Maybe the girl has been in the museum for an hour, was already there 45 minutes ago and looked at the piece but then was waiting for a friend in another time zone to have a break. When the couple arrived, the girl and her friend were discussing in detail the Monet work that they are both completely familiar with. How about that?