I'd be in the try it camp (with an agreement for the length of time before reevaluating). To be clear, I am projecting some of my own biases, particularly about girls being so friend focused that they hide their smarts (there's a fair amount of research on this point, which might suggest that there could be some social reason she isn't complaining about the work being too easy). That has long-term implications.
If her friends are going to treat her differently if she takes math in another room, are those really long-term friends? What's the lesson there?
This is of course, completely a family decision. Note though that it is pretty unusual for a teacher to proactively approach a family with this suggestion. I'd be sure I understand that teacher's thinking and what she/he is observing.
