If a girl smiles at you when she sees you what does this mean? Because I'll be walking to my locker, she'll be at hers we'll look at each other (not eye contact) for a few seconds and she'll smile. Would you keep looking at someone who is looking at you for a few seconds normally or just look away after a second or so if you didn't like them? Also whenever she smiles she's the first one of us to smile and will usually wait for me to say something first (she is a bit shy). Do you think she could like me? Also when I talked to her outside of school she gave an enthuiastic hi and had a big smile and when I said hi to her today she smiled and said hi back. Also when she smiles she usually shows her teeth and not just a regular smile if that means anything and also if I see her walking towards me sometimes she'll just give a small closed mouth smile (no teeth).

BQ: Is it true that girls will give a different smile when they like someone than if they are just being friendly and how are they different?

Also how do I show I'm interested, should I walk with her to class (we have the same one) just say hi to her or what?

It sounds like she may like you...but you can't totally tell just from a smile. Yes, you should definitely walk her to class and start some kind of conversation. But from the way she smiles and looks at you, she probably wants you to talk to her, so do it!