1. Wealth/Family History
In an upcoming episode it will be established that Barbara's father is a very wealthy and powerful man in the city, and her family is part of Gotham's high society. In the comics, Katherine Kane's family is just as rich as the Wayne Family, owning all of what the Wayne family didn't already own.
When a writer from The Hollywood Reporter indicated to the actress that he thought Barbara would become Batwoman in the future, the actress had this to say: "(Laughs.) I honestly don’t know! We only get the scripts a week before we shoot. I have a vague idea of where things are going, but I have no idea [about that]. You’ll have to watch and see! (Laughs.)"
2. Relationship with Renee Montoya
In the comics, Renee has a very tortured past with the Bat-Woman. Being the first love of Renee, Kate has an overwhelming power over Renee, which she never quite gets over. This is further complicated by the fact that Kate and Renee ended things in a bad way- leaving Renee quite isolated.
From the pilot it was quite clear that Renee was still in love with Barbara, whereas the future Mrs. Gordon was still struggling with her past. In order to build on the character of Renee Montoya and get her to the point where she could become The Question Katherine Kane would have to be involved at some point. But since Batman is still a kid, Batwoman surely can't make it onto the sceen before him.
Erin Richards had this to say about the relationship between Barbara and Renee, "We’re not entirely sure what that relationship was. It’s not been revealed where that will go. We talked about it [ahead of time], and I said I didn’t really want to know long term where it was going. But we talked about where it has been — I’m trying not to give anything away. (Laughs.) Renee Montoya is a factor in Barbara’s life, and it’s something that will creep up and cause problems between her and Jim. You’ll have to watch and see what that means."
3. Her Personality
Erin Richards had this to say about the character she is playing:
"We discussed a lot about Barbara and who she is. I think she’s got a lot of different sides to her. There is her proactive side; she’s completely in love with Jim Gordon; she’s completely intelligent and a strong, bold, committed individual. When things come up that she reallywants to fight for, that she really believes in, she’ll go hell-for-leather to get them and to steer Jim on the right path. But, because Bruno is so fantastic and writes these incredible female parts, she obviously has this total other side to her — this dark past that she’s hiding from Jim and from herself, essentially, with all these layers of intrigue and mystery."
Much like in the comics, Katherine Kane has a lot of different sides to her. Appearing as a Gotham socialite in real life, her hidden persona of Batwoman appearing to be a complete contrast from her personal life. Perhaps Barbara's interest in justice and law and order will develop into a much stronger desire to make a difference. Although we won't be seeing Barbara become Batwoman- we could see her doing everything but.
4. GOTHAM is changing things up a LOT.
By changing the age of characters, the writers are moulding the various plotlines from graphic novels set in Gotham to become included on the show. Taking any plot, origin story, or character arcs that aren't dependent on Batman's presense- and incorporating it onto the show. Although many people are protesting such changes, its highly beneficial for comic book fans in general because this way DC/WB can introduce beloved Gotham-centric characters to audiences in a new light, and give them the screen time they need to become fan favourites- just as they have for comic book readers. This will allow them to use more Batman characters on film without the need to spend hours showing their origin stories.
Thus, considering the character Barbara Gordon has been overwhelmingly vague in the comics up until this point, it gave the writers a great opportunity to take elements of Katherine Kane and incorporate them into Barbara's past and present. We all know that Barbara's relationship doesn't work out with Jim in the future, but this new path will give us an additional depth into why that relationship was doomed from the beginning. Although, I must stress that I do not expect Barbara Kane/Gordon to become Batwoman on the show... I do expect her to be a major catalyst in the development of both Renee Montoya and Jim Gordon's characters... and thus Katherine Kane's character gives the writers the ability to do both at the same time.