In your situation right now, you have 2 ways to choose:
1. BE SUPER NICE. Treat her lunch, talk about her favourite
subject, compliment her, etc. Don't expect anything in return
immediately but by being nice, who knows that things will get
better between the two of you. 
2. BE SUPER NASTY. Try checking up on her every single day until
she gets tired of it. Ask her persistently 'what do you eat?',
'what are you wearing?' and so on. Let her taste her own medicine.
