She's an absolutely dreadful actress.
Every time I see her, I am always like "Wow, more feminine looking Bieber really sucks at acting."
I think she was trying to be intense and intimidating like you'd expect a Bat-family character to be, but it just came off as stiff and mumbly. At least she didn't do some sort of awful Christian Bale bat-voice when she was in costume. Though I suppose with all the ribbing Oliver got about that from Barry and Kara they kind of knew better than to go down that road with someone else.
Also the conversation betwen her and Kara was kind of awkward as Kara talked about Batman and how him and Superman know one another when I was fairly certain that it was established that none of the heroes who exist on the Flash/Arrow Earth exist on Supergirl's Earth and vice versa. And even if Batman did exist in both places, it'd be weird for Kara to talk about Superman knowing him since he clearly wouldn't know the Earth-1 Batman and the Earth-1 Batman wouldn't know Superman since Kryptonians don't exist on that earth.
Which is another reason why it would make sense for them just to bite the bullet and collapse the multiverse enough to the Supergirl show in the same dimension as Flash/Arrow/Legends and be done with it. I mean given how infrequently the other shows interact with one another it can't possibly be that big of a concern to suddenly have more heroes and villains native to Supergirl's dimension, or aliens running around in the same dimension as Flash/Arrow.
Finally the ending made it seem like we won't be seeing Superman again for a
long time. Like longer than next year's crossover.