Night could see why the professor didn't use real animals. Too much risk, honestly. Students would take them out as pets. With a charm, that could happen too, but they would eventually revert back to their original state. It was just a charm. Would saying that help or would she come off as rude? She had a different idea.
"
Over the summer, we can go to Diagon Alley and buy a similar one. For the rodent area in the common room. I mean, unless you get clearance to keep her in our dormitories." Hopefully that would work.