Any girl knows why? and can help?

There is this co-worker I have a crush on....I thought she has a crush on me too because she flirts with me a lot and she said i m very cute. She usually sit with me during lunch however, recently she stop sitting with me. She sat on her own table and let other guys sit with her. I umed she no longer have any interest in me but sometimes when she pes by my desk she try to start a conversation with me. For example, she came up to me showing me her nails and ask is the color pretty? or she came to me showing me her new phone. In addition, my bday is coming up and she came to me 2 months before telling me she will be taking me out so don't plan anything on that day. Anyone knows why she did those things? Does anyone think she still like me?