What should I do next? And what is my current situation?

Hi,
I've been seeing this girl for quite some time, we usually just say whenever we walk by or see each other. So I saw her last week shopping alone and I was with a friend, so when I saw her I went up and said hi and chatted for a bit. Coincidentally, when I left the shop, we were parked near each other so she finished unloading her cart and I decided to offer to push the cart back to the rack so she wouldn't have to do it. Whenever we come across each other, she would smile and say hi. We were in the library the other day and she had a quiz to study for so I decided to let her study. When I got home, I messaged her on Facebook and asked her how the quiz went. She said it was good and said "thanks for asking me!" So I responded with, that's good to hear, looks like your studying method worked. She saw the message and hasn't replied since then.