Im like a 16 year old but im not sure if she likes me?

okay, well i like this 17 year old girl and im 19, but im not sure if she likes me. i once told her that i like her and i ask her if she likes me but she said she don't know. she flirts with me an all so now im confuse, we work together and every time i talk to her she gets real happy, sometimes i try not to put too much attention to her at work but she gets sad and i seen her glance at me with a sad face. so when i try to talk to her outside of work she acts different, when i text her she takes too long to answer and her text makes me feel that she don't want to text me, i seen her sometimes at the club and she ignores me. but at work she is totally different. so i dont know what should i do?