Strictly speaking, Nightmare's physical abilities were far superior to Batwoman's.
After all, it was a supernatural creature born within a dream and possessed a Healing Factor. Unless it was completely killed in a short span of time, that immense vitality meant countless possibilities.
Batwoman possessed physical abilities beyond human limits, but they were still merely the limits of an ordinary person. This brainwashed Nightmare, on the other hand, had simply given up on being human!
Its brain was not particularly sharp, but that was not a problem. As long as Harley had brains, it was fine.
Playing games alone was a little boring, and talking to herself all the time was a bit too deranged. Harley had brainwashed a Nightmare into becoming her little lackey; at least she now had someone to chat with.
And it should know the enemies' plans, right? So she could also use it as a walkthrough.
Hypnosis, as a means of control, was not very stable. She needed to reinforce its psychological suggestions from time to time through words and actions, keeping it under control.
"Alright, Batwoman, what's your next plan?"
She raised a hand and patted Nightmare on the shoulder, another physical gesture of psychological suggestion, as the doctor asked.
"Find Insomnia, beat it up, and send it to Arkham!" The hypnotized enemy blurted it out without hesitation. It was a very Batwoman-like answer, though the tone felt slightly off.
When the real Batwoman spoke, there was no emotion to be heard beneath the low rumble of her voice modulator. This Nightmare version, however, actually carried hatred in its voice whenever it mentioned an enemy. That was the difference.
"Oh my, what a wonderful idea. So, do you know where that Insomnia fellow is? I'd like to give it a little present too."
Her