Why does this girl act as if she likes me one day and act as if she's disgusted by me the next day?

Anonymous
I'm "best friends" with a girl that I've known for 3 years. The first year we knew each other she would talk about wanting to date me and she almost asked me out but then changed her mind because she was scared of relationships and she had just gotten out of one, and i understand that and was fine with that.
Fast forward a year and she finds someone else she likes, which ends up being a shitty person who was exploiting her. Then another person shows up the same, and then another. Each person is worse than the last and she's gotten really hurt by them and I've done all i can to support her (i have to admit i probably am not much help no matter how hard i try).

During these times she'd always say how I'm an "exception" or I'm "different" in terms of how i can act towards her. She says things that suggest she's interested in me for example talking about how i shouldn't cheat on her even though we're not dating or how she has dreams of us being married or living together, or something as far as "Well I'm not gonna ask you out so you gotta step up your game" when one time we were talking about how we're both single. she always talks as if im already her boyfriend or she wants me to be her boyfriend but if she does the next day she will always and i mean always act the opposite. If one day she says she find something about me attractive or compliments me (which isn't often) the next day she'll say something contradictory to what she said.
One day she'd talk about how she wants me to take initiative and ask her out someday and i say I will (we're long distance and i want to ask her out when we meet and I've told her that too) but the day after she'd say how stupid we are for talking about something like that.

I don't know what it means when one day she's seemingly interested in me and the next day im suddenly this cringe, weird, "never had a chance" type of guy to her. it's extremely confusing and even draining. I like her but the way she acts makes me think she doesn't
Why does this girl act as if she likes me one day and act as if she's disgusted by me the next day?
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