I don't know if I'm remembering correctly, but wasn't she allowed to join? Because even though Beru defeated her, Jinwoo didn't outright say 'No' just "Why do you want to join?" and then he asked if she was interested in him (romantically) and honestly, if I was someone working as the leader of the company and someone wanted to join because they had a crush on me, I wouldn't let them?? That's just irresponsible and they'd be super unreliable.
Anyway my memory's super hazy so I have no actual recall of the scene because romance bores me but I think they did let her in? I think she was shaking, not because she was mad but because she was jealous.

Bruh i can't even imagine how mad she is, she really tried hard to convince him but she still wasn't accepted in the guild and then someone else just joins. Feelings could also be involved but I would be primarly pissed.