Okay, listen. I'm drunk, so obviously, I'll be the best source of wisdom here for you.
She's obviously taken an interest in you, given that she dresses that way. There's only 2 reasons she would look at you that much. One, she thinks you look freakish, or 2, she thinks you're attractive. It's probably 2 in this case.
Strike up conversation. Doesn't matter where, but a quieter setting would be best. Look for an opening for conversation. EXAMPLE- you see her listening to her iPod or something, Go up to her, ask her what's playing, look for bands you both like. Introduce yourself. BAM. You are acquainted, and you've even found common interests.
If you can, find a seat next to her in class, if you don't have assigned seats. If you do, wait for a group project and ask her to be your partner, so you can spend some time with her and you'll get to know each other better.
Just find common ground between the two of you, then once you've established compatibility, ask her if she'd like to see you outside of a school setting, e.g. on a date. From there, the ball is in your court, and it's up to you to decide if you want her and you can get her. Don't waste time being shy, trust me. If you do, someone else will snatch her up.