wasn't penny one of the healers for his mum? in any case, weasley association aside, he doesn't actually have reason to be mean to penny. so he probably won't be mean. he's learned to shush his face where matters of blood are in question.
draco would like to point out that she did just date a murderer and basically make an entire band and their fanbase hate her, so whether or not she thinks he's a prat is irrelevant. i mean, not that he would actually know any of this or care. lol i'm sure they could find some strangely common ground in the near future.