Model the behavior you're seeking and see if she follows.
Wear a set of headphones next time you go.
When you make eye contact with her and she smiles back, take your headphones off to indicate that you're willing to interrupt your work to talk with her.
If she takes her headphones off, then you have your chance. If she does take off her headphones, keep this chat very brief unless she seems obviously eager to continue. Say "Hi." Measure her response. Everything you say after that is on you.
If she does not take her headphones off, try again some other time; she might not have time for a conversation at that moment.
If you try a few times and she never takes her headphones off, move on.