relationship advice

hi guys i'm new to this!!

basically i need advice.

i met a girl and we have became friends and have been for almost two years. we occasionally see each other outside of work.

in the past she once got a taxi home with myself and made a comment re: being unable to unzip her dress when she got in and asked would i oblige in unzipping it for her, being a gentleman and not wanting to jump to conclusions i aided her request and she left the taxi giggling. taxi driver was laughing he was convinced it was a come on, i wasn't so sure but i'm always blind to these things.

a few weeks later the girl passed comment that she had gone for ages without sex and thought she would have had it by now; was this a hint that it was a come on the previous week??

the girl in question always passes comments in a joking manner that she doesn't want to be left alone with me in case i try it on (she is laughing whenever she says this.)

recently it was this girls birthday and she kissed and hugged all the other colleagues (all female) and said i'm not giving you one you may get the wrong idea (again she said this smirking.)

my colleagues all believe this girl is after me, i don't know what to think. all i know is i do find her attractive both mentally and physically but would hate to jeopardise our friendship if i made a move and was wrong.

any thoughts/advice people, i'm starting to go crazy