What girl doesn't love to feel pampered and special? Spoiling her a little can't hurt your case, and there's a very good chance it will help you get in with her, especially if she's had boyfriends in the past that didn't treat her as well as she deserved.
Buy her little gifts to show you've been listening to her -- the charm bracelet she loved in the jewelry store window, or the T-shirt she told you she wanted to get for herself. You don't have to spend a lot of money. Even a small box of her favorite chocolates shows how much you care. Just don't get too intimate: Lingerie is way too presumptuous for this stage in your relationship, and it's more likely to get you slapped than kissed.
If you want to really make your friend feel like a princess, set up the perfect evening for the two of you. Pick her up in a limo and take her out to her favorite restaurant. Once she's buttered up, you can tell her how you really feel about her (see No.1).