Are my feelings for her justified?

I fell in love with a girl. And because of this I closed one eye to all the red flags and warning signs about her. But turns out that she never cared about me, nor anyone she's been with. At all. All she cares about is her and having someone there to make her feel better about herself. Which is why she replaced me so quickly with someone else. I can't help but to feel mad, jealous and hurt. I mean I really fell for this monster and she dropped me just like that.

At the same time she gets angry when she finds out I've been out with another girl (a friend). What is her deal?
Are my feelings for her justified?
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