So, my advice is, like many others, leave her a note. Or, be a little more clever and leave her something like the picture below in a message screen or a note taking app so she can respond, and see how she acts. Put the phone on her desk as you walk by, sit back down, and when she looks at you, ***smile back like you always have***. I did this in a quiet library with a lot of people, and it started the conversation, plus she said it was really cute. Nobody else cared. 
***It also gave her control to start or stop the conversation.*** 

[!["Hi! My name si (insert your name here) What's yours? Btw, cute headphones! :)"][1]][1]

 

  [1]: https://i.sstatic.net/pm4Zs.jpg