According to cbr Whedon wanted to use the original 1967 comic Batgirl origin as his source material. The comic is in DC Showcase Batgirl Volume 1 which I have.
Its based on coincidences.
1. Barbara Gordon is going to a masquerade party.
2. Bruce Wayne going to same party but not together.
3. Killer Moth Gang Attempts to kidnap Wayne heading into the party.
4. Only one witness. Gordon dressed as Batgirl.
5. She is an expert in judo and other fighting skills and gymnastics. Why? You would think she would be a cop, martial arts teacher etc. Just a brilliant librarian.
6. She alone beats the kidnappers because zero witnesses. Where are the other guests?
7. Batman tells her she is a female and not a crimefighter. I hope Whedon dumped this part.
8. Batman and Robin get a letter from Killer Moth addressed to Bruce that he needs to give 100k. Really? A multimillionaire just going for pocket change. You would think he would want to blackmail for at least a million. Stealing and reselling one of Bruces cars would have been easier and would have gotten mire money. I assume Bruce buys expensive cars.
9. Barbara has a book that Bruce wanted so in her motorcycle rides to his house. eaNow coincidently Barbara has her costume as part of her clothing. Also coincidently Killer Moth showed up to Wayne Manor seconds before.
10. Babs hears a gunshot then sees Bruce shot dead. She changes her costme and enters. It was a dummy to look like Bruce.
11. Fight ensues. The dynamic trio wins.
12. At end James Gordon tells his daughter he wishes she was more like Batgirl.
Which makes me wonder. Does James know his daughter is an expert at judo and gymnastics along with being a costume designer? Do they talk?
Whedon needs a different job. This is lame. Too many coincidences and story would have worked better if Babs purposely wanted to fight crime not getting into it because of a coincidence of timing and discovered she liked it.
Horrible source material. Barbara storyline should have had her wanting as a child to fight crime like her dad’s friend Batman, become a cop then decide to become a caped crusader. This source material relies on coincidences and wonder her relationship with her dad and why she became a judo gymnastic expeer.
I would start the film with Commissioner Barbara Gordon aka Oracle talking to Selina and Bruce’s daughter about becoming part of the Bat Family then flash back to Batgirl’s start.