Why is she so confusing.......????

There's this girl whom i like and we are having a good rapport.....there are days when she is all flirty and very suggestive giving hints and all....and there are days when she's just like an acquaintance.....this see-saw mode of her's has continued for long a time.....she has a BF and often have heard her fighting with him over the phone......I don't know what to make out of it....???? I tried talking about awkwardness but she never wants to making it even more awkward.....Wat's going on in her head??????