If she still talks to you as usual, after others joked about you, then she probably likes you. If it's her first time as well, she will need time to think and understand her feelings.
Get close to her and find a reason to be with her often-form a study group; go to see Kandy town; boat ride; Pera gardens.... whatever. Show that you care. Drop her to her boarding place after lectures-this works almost always. Talk about common issues like good places to eat out around the faculty etc. Ask about her family, school life etc. These things show that you are interested in her. And of course, love shows in your eyes and complexion when you look at your loved one, in your voice when to talk to her-she will pick it before she notices your 'chiththa tharanga".

If you have a close friend, get him to joke more about you and her, in front of her, and among your common friends. This will get the message across to everyone around-including any other prospective candidates.