Smiling is fine, as long as its friendly, and doesn;t make her think you are wondering how she would taste between two slices of bread!
Seriously - next time you see her, say Hi. Either she will stop and exchange a few words, which may mean she is keen to get to know you a little, or she will say Hi to be polite, but not stop walking, which also sends a message.
If you have a chat, be light and friendly, and then the time after you see her, see if she'd like coffee - and from there you will know how interested, or not, she is.
The golden rule with girls is - if she is interested, she will let you know - no signs, no interest.
Good luck.