Reword: Imprisoned in an apartment with a complete stranger, a humanitarian twenty-something has to a find a way to save the world and its population before her abductors’ plan unfolds.

I made a new logline for it:
https://loglines.org/logline/reword-2-when-she-is-abducted-by-her-estranged-father-so-she-can-be-spared-a-stubborn-humanitarian-must-find-a-way-to-prevent-him-from-killing-most-of-humanity/

I made a new logline for it:
https://loglineit.com/logline/reword-2-when-she-is-abducted-by-her-estranged-father-so-she-can-be-spared-a-stubborn-humanitarian-must-find-a-way-to-prevent-him-from-killing-most-of-humanity/

Agreed with Dkpough1, you're better off describing a character flaw than the age.
What you suggested are not flaws:
? Too demanding of herself (is there an adjective for that? Such as self-judgmental)
? Fixated
? idealist
? self-judgmental

A flaw should be a negative quality, one that would require hard work to overcome in order for her to be a better version of herself. For example: arrogant, self-centered, elitist, etc...

Otherwise, this logline is vague in terms of stakes. Sure, you wrote that the world is in danger, but why and in what way? Do the bad guys have a nuce? A bio bomb?
The nature of the danger they pose is important for the concept, as it will explain what kind of bad guys she is up against.