She most likely doesn’t have a crush on you.
She does have a boyfriend. Oftentimes, this means that a girl is not emotionally available to you.
She has only stared at you a couple of times. This doesn’t indicate a pattern of behavior.
Even though she usually smiles when you both greet each other, she most likely does it to be polite.
There is a good chance that she smiles at other people that she greets, not just you.
When she ignored you and acted as if she didn’t see you, she may have simply been having a bad day.
Perhaps there was something on her mind that day that was bothering her.
She may have ignored a number of people that day, not just you.
It is best to move on.
Again, she does have a boyfriend. Even if she were to suddenly start liking you out of the blue, her boyfriend would always be a complication.
It is best to pursue a girl who isn’t in a relationship.
This way, the both of you can interact with a lot more openness from the very start.