Hello! I'm Alissa, and I've got two here. First is Romilda Vane, two years younger than Lisa and from Gryffindor. I can't think of a reason why they would be acquainted unless Lisa frequently goes to Gringotts where Romilda works.
Second, though, is Roger Davies. He's also a Ravenclaw and a year ahead of Lisa at school. They would have at least known of each other, but he tends to gravitate towards the females of the school as friends. He just connects better with them, thanks to his many sisters. I could even see them dating at one point, but that is definitely up to you. Just offering Roger up. He's the kind of person who likes to remain friends after the break up, though. He also works at the Ministry, so there's interaction there, too.