Is she playing hard 2 get?

this girl (18) @ my work knows i (21) really like her, we work in the same building but hardly talk cos of work. we often catch each others eyes, she pokes her tongue out all the time & smiles alot, and cos im leaving this job soon, i asked if she wanted to go for a drink, and she said yes:) HAPPY DAYS! BUT why would she sound interested in goin 4 a drink, xchange number, then pretty much aviod the topic when i text her or come across like she dont feel the same way? i said that im not goin 2 keep pestering her if she dont want to go out, but she still said that we can go out, but im not sure if she wants to or not? cos i think i might be too 'pushy', but then i feel like its always me initiating the txts, why cant she txt me? i am totally confused by this. n e way, i sort of left it with her to txt me if she wana go out? right or wrong??? need good advice!!! cheers peeps.