The "your mother wants to see you" line was purely so Hermione could navigate both herself and Fleur out of that absolute train wreck of a conversation. Her life was way too complicated to ever hold out hope that Fleur and Clara would ever get on and she made the mental note to at least get them on "I-don't-really-like-you-but-will-keep-a-civil-conversation-with-you" terms. At this point, her hair would go grey by the time that the pair of cousins managed to be nice to each other.