I has a similar situation with TS, an elder girl in her early 30s, colleagues, she's career driven but at the same time a very sweet and friendly girl... we became very close, clicks well, then i fell in love with her... Did things such as dating her out one on one during weekends, buy her small gifts to make her happy... always chatting and msging over the phone at night...

but there's always a hidden part where she would date another guy secretly who she would hide from all the other colleagues including me...

Overtime the truth came out, she is actually in a relationship with another guy (not the secret date)... so I guess she is just keeping her option open for a better person to appear in her life... which I don't think I even stand a chance... I gave up and moved on... But i still keep a healthy colleague relationship with her... She noticed the change but I guess she just couldn't be bothered with a small fly like me...