When you like somebody and you show it to them (her), they usually like you back. She may like you just as a person, a good guy, or as a potential lover/BF.
She may not be sure whether you are just a regular good guy who showed an interest in her, or whether she can consider you as a lover/BF, so she is testing waters. She is checking out how you are behaving, who you are talking to, who are your close friends, if you have any enemies, what interests you, if you talk fast and loud, if you are shy, if you are around a lot of girls, if you are creepy and chasing her, what you like and dislike and so on.
She is observing all of this by monitoring your behavior. You may not even talk to her but in her head she already has a good "picture" about who you are...
If she doesn't care about you being a potential lover, she will most likely slowly drop this behavior. She will disappear.
On the other hand, if she sees you as a potential lover, she will let you know in many different possible ways and subtle hints. There are tens of different ways, for example: She may come closer to you couple of times. She could be talking loud on her phone so you can hear her (and notice her). She may bump into you by coincidence (there are no coincidences), or she may touch you in any way. She may stand right next to you, or I front of you, perhaps just showing you her back (or rather ass, LOL). She may start talking to your friends, even asking them about you. She will be looking at you longer than usually, in your eyes and even smile. She may put nicer clothes than usually so you can notice. She will even wear the same color (or shirt) like you - you have a blue today, she will come in the same blue color tomorrow. You have rolled up sleeves today, she will have them rolled up tomorrow and so on. Or she may mirror you in any other way - you say that like that movie, and she says she loves that movie, it's her favorite one. If she is bolder, she will even come directly to you and start talking to you.
It doesn't have to be all of the 'clues', but if you see two or three like these she is most likely interested in getting to known you better....
