I know I mentioned Malou to you in pm, so the others I have:

Somersby Fudge was Ravenclaw class of 89 so only two years behind her. She would probably know him. He is currently a curse breaker intern for Gringotts and is the oldest son of the owner of the Sanditon Resort. I can always send him in for injuries or what not. Also, he is available for hurling but not sure how Donna would feel about a younger guy.

I am sadly lacking on hurlables or friends (that she would already know) that would work for Donna at the moment. For new friendships I have @"Dahlia Potts" who is one of the daughters of the owners of the Potts Flower Shop in Hogsmeade and just graduated this past spring from Hogwarts (Huffelpuff).

Somehow, my only WC is a vampire so I'm not sure that would help you at all. But if you think of something with her I'm always looking for things for Galina to get involved in (which is how she ended up in prison for a year for a crime she didn't commit - whoops).