Comic book movies/TV shows - best not to think too hard about realism. Luke became a 2/3 Jedi by spending what felt like a weekend on Dagobah with Yoda (or else the Millenium Falcon travelled at sublight speeds for months or years to reach Bespin)
Luke was there at least a month, and being a Jedi is kind of supernatural. That's why I have no issue with Courtney doing the exact same thing she did with the cosmic staff. That staff is an equalizer.
Luke was an adult, and with the Force, could probably handle himself in most situations after a month of lessons from Yoda. Of course, he got his ass handed to him by Vader who showed him what it's like to face someone who was really trained.
And yeah, I do think that they were stuck in the Falcon for weeks minimum.
But that's another issue.
What Courtney did was like Gabrielle on Xena. She went from not knowing a thing about fighting to being able to beat anyone who wasn't a main character in one episode where she was basically just handed a stick.
Or Daniel LaRusso somehow being able to beat about 6 black belts just to beat a 2 time champ because he trained for 6 weeks.