>> Buying chocolate from her will make you just another customer.
Ever heard of getting your money's worth? Three bucks is pinch if orz can use it to make an opening with her. By buying the chocolate he can get her to;
Notice him.
Make her realise that he's interested in her.
Make small talk. Ie: Following up buying the chocolate he could ask casually "How the the fundraising going..etcetc".