A college grad stuck in a dead-end job impersonates a tech “it girl” in order to get hired at NYC’s hottest startup, but when the company is secretly in danger of folding without a game-changing new product, she learns she has more to offer as herself than she knew.

Another edit based on your notes - thank you! Let me know what you think:

When a twenty-something, desperate for her real life to begin, lies her way into a job at NYC's hottest startup, she must prove she belongs there by saving the company before a jealous co-worker unravels her lies and blacklists her from Silicon Valley.

As above, your Logline isn't bad had some good irony, I can see the conflict, but maybe just say: but when she's put in charge of creating a game changing product to save the company, she must pretend she's the boss of a fake company to trick real IT whizz kids to create it for her.

Basically, although I see the goal, I don't get a sense of the conflict in act 2. So she learns she has a lot to offer, but that is the arc rather than the action that leads to the change

Check out the guidelines for writing an industry standard logline under "Formula" at the top of the web page. Loglines are about actions taken, not lessons learned about life, or inner strengths or weaknesses. ?Loglines are about how the protagonist struggles for a specific objective goal and the main obstacle or antagonist who stands in her way. So:

With the company in danger of going under, what becomes her objective goal?
Who/what stands in the way , who/what ?threatens to defeat her achieving that goal?