If you havin girl problems, I feel bad for you son.
Zero, don't ignore her.. you havn't even properly got together yet so the only thing you're achieveing by ignoring is driving her further away and putting yourself completely out of her thoughts.
Basically, if she's acting nice on MSN.. just ask her how come she never talks to you at school? You will be able to tell whether she likes you or not from her answer. At 16 most girls are all shy and awkward about meeting boys for the first time, (especially if they fancy you) which explains why she's so talkative on MSN.
Also, if she's with her friends, she definately doesn't want to go through the whole introduction thing in front of them.. it's embarassing.
So yeah, just talk to her more on MSN and say you want to meet up after school.. then BAM, thats you in there
Pretty bad advice from most people, really like.. you're all hopeless virgins.
I can't believe the idea that "you might not be priority on her list".. what kind of self-righteous asshole has a priority list? That's probably the most pathetic thing i've ever read. My advice, if you ever find a girl like that.. kick her in the ovaries.. repeatedly.
If this helps and you need anything else, hit me up with a PM.