The Oxford English Dictionary is a resource that requires a subscription to use. Now, if you are using a library or college network, they often pay for a subscription for the OED. It's a fantastic resource, however, there are issues here. Three...exactly.
1.) Buying the full 20 volume set is around $1200.
2.) Buying the compact OED is around $400.
3.) Buying an annual OED subscription for an individual is $90.
Now, _virginie_ is right about procurement. However, since the OED is behind a paywall, what I would have done, and what would probably be the best thing to have done for the sake of argument, is to screencap the OED definition of girl and post it here as attachments. Then, it's there for everyone to see, especially as it is being used as a reference point.
Understanding the OED and the manner of its use, I decided to utilize the Etmology of the word girl. While OED is a lot more academically credible, it is just one tool, albeit a powerful one, for the study of Etmology. Now...in that examination, the majority of uses involved age as a codifier. In society, age is used as a mechanism to discredit or negate someone, via maturity or experience or what have you. There's also the long standing tradition of youth expectations being that they are subservient to their elders.
Now, people are all about context. The word girl isn't derogatory, and nobody here is being 'triggered' by its usage. The contextual use of the term matters. But what I think some of the argument being lost here is that this about its contextual use in terms of male sexual objectification and male possession. Chicago's boyfriend calls her girl, but the context of that and their relationship also means that in serious conversations, he's not referring to her as a girl, or his girl. It's about the possessiveness, the ownership when used in such contexts that is being argued. The video posted was about objectification. And given age and that, it comes across weird that Bilak is referred to as girl and not woman.
This isn't trumpeted outrage though. It's just looking at how we work and treat people. Not everyone has to agree...but it's not some off the wall feminist concept that is destroying western society.