If you can't "bust" her watching at you for at least 3 times, she is not interested.
Expectations are killers. You could approach her and push for a conversation but those convo's are usually too awkward unless you can act like a man who's intention isn't about approaching/hitting up.
If you can 'show' you are living decent or are having a good time, you'll seem more trusted and likeable and people would be more likely interested in talking with you.
So your body language matters. As soon as you are seen you would be like a "dot" on her radar, there is nothing more than to just going with the flow and expect nothing. If your paths do cross somehow with a cause, the conversation would be different right. As you wouldn't have to push for a conversation and there is nothing weird about crossing eachother paths. You wouldn't look like a dude who tries too hard and there is no lose in asking how she is doing and how she has been doing lately. Maybe she has something to share, if not, don't push it but be a man and see that all conversations are easy come and easy go.
And yes, not everyone will cross you path, sometimes you just let it go. Something you let it "happen".
So unless you got something important to discus, i wouldn't approach it. Being a little bit selfish is not bad as this would show that you know what you want vice versa.
Show that you are in control of your body by sticking to your own rules. Say no to the things you do not want. And don't joke around too much, it shows insecurities. If you really are into this girl, find out more about her as this would give you a little advantage in keeping a conversation up. Your interest in her must be genuine, or she will find out and be bored with you anyway.
Someone once told me as a kid: "You shouldn't bother your time with people who wouldn't do the same for you."
This is something that helped me through some times. As i would live more for myself and started seeing the things that do not matter.
