She Loves Me, She Loves Me Not

Liking girls can be hard. One moment, you are almost positive that she likes you back. The next moment, she is completely uninterested, and you ask yourself if she even knows who you are. There are three usual reasons:

She likes you.
Stereotypically, she expects you to make the first move. She's into you, but she doesn't want to make that too obvious, in case it turns you off. That's why she acts uninterested sometimes. But sometimes its hard to keep all the emotion in, and she can't help but to be interested. Or maybe she likes you, but she isn't sure whether or not you like her back. She might try to stop herself from liking you, hence the lack of interest sometimes. But if she likes you enough, you'll still be able to pull her back like a magnet.

She's playing hard to get (i.e. she likes you)
Many girls believe that the way to keep a guy on his toes is to play hard to get. Keep him curious, keep him questioning whether or not she really likes him, let him do the chasing. And if you're here reading this, chances are that it worked. She really has got you wondering whether or not she's interested. Obvious signs are: flirting with other guys, looking into your eyes across the room for a while, then quickly turning away, asking you many questions about your life and such, then suddenly acting disinterested, days of heightened conversations, then nothing.

Face it, she doesn't like you.
Sorry to break it to you, but maybe she's just not into you. If she's smiling at you from across the room, maybe she's smiling because she's happy. If she's blowing kisses at you, maybe they were meant to be for the guy behind you. If you hold her gaze often, maybe she just forgot to put her contacts on, and she doesn't realise she's looking into your eyes. Always keep this option at the back of your mind, don't fall for false hope. However, if you really do like this girl, this shouldn't stop you. Keep trying! You never know, maybe when she finally does notice you, she'll fall in love!