This girl is the worst and deserves to be dumped..
Depends on which route MC want to take really, this type can also become the most obedient 'pet' if the story want to go there.
Something like this:
She's being all confident because she think herself center of the world.
But once confronted and made to realize her own belief is wrong.
She become so insecure since her whole world just came crashing down.
And ironically the one person who told it straight to her became the only one she can trust.
Which make her all the more desperate to not get discarded at this moment.