Hi Kanishka,
She may be looking at you but not smiling because she doesn’t want to make it obvious that she likes you.
If you have noticed that she keeps on staring at you, she may be hoping that you get the message and approach her.
She is most likely not going to approach you.
Even though you stated that it is absolutely not normal to say hi to someone that you don’t know in Sweden, remember that you still go to the same school as her.
Thereby, you aren’t a total stranger.
You are both schoolmates.
You could approach her and start a topic that is related to school.
Using a topic that relates to school will help to make your approach more natural and less awkward.
The sooner you do this, the better of an idea you will get on whether she is truly interested in you or not.