Well think of how you'd like to be treated if in her shoes. Say hello to her when you do see her. Invite her to join you guys at lunch or where ever. Discreetly see if one of your friends might wish to date her. By all means you have to be willing to date her not humiliate her. If none of you boys is attracted to her don't set her up to be hurt. In order for her not to feel led on by you, hang out with her and her girl friends with your new gf. You'll want it to be obvious that you're not wanting to date her or be in private with her. Buy her lunch if you guys go out to eat, once in a while. It's going to sting to be rejected but we all have to learn we don't always get what we want. Again think of it if you really liked a girl and she said no thanks but let's be friends. She'd hang with you but keep her bf close. IF!! you don't want to be her friend and really don't like her, you still need to use your manners but you don't have to hang out with her or closely socialize.