Millicent Voletta Bulstrode is a current graduate of Slytherin in 1998. She is known to be a pureblood and she used to be a bully due to peer pressure. Millicent stopped being a lamb to Pansy's gang in her fourth year because she had her own goal to work as an Unspeakable when she got older.
I think it's important to mention that her ideals changed after the deaths during the final battle happen. She was also one of the Slytherins to come back and help the wounded but did not fight.
As the moment, she's working as an intern there and makes pretty good money. Millicent's not a bad person but she's stubborn and thinks there is nothing 'good' about her.