I have Marietta who is a dark-leaning, pureblood though she pretty much is looking out for herself (and Padrig on a good day). She would be nice to most former Ravenclaws to a certain degree. Marietta niceness is rather relative. She is Umbridge's secretary at the Ministry and a general overachiever. She is a slightly different sort of brown-noser in comparison to Percy though.
She is open to lots of random stuff with everyone. Her romantic interest pretty much is Padrig even if they are currently off and not on - their version of off is slightly gray. She'd love friends and enemies though. Backstory galore.