Girl gives lot of IOI's but gives Facebook instead of number

I met this girl and she gived me a lot of IOI, then SHE added me on facebook without even asking me my full name ecc. The next time i see her i ask for her number after some flirting (she was with a female friend) and when she was leaving i asked for her number.

She replies: "we have Facebook we can chat there, ill write you"

Ok shes not interested or its too soon for telling that?

Thanks