This fight should look familiar--it's your typical "oh no, you're dazed and it looks like there are a bunch of enemies even though only one is real" trope. The good news is it isn't too difficult to deal with once you learn the trick.
Trying to simply punch your way out of this fight is technically possible, but the battle is much easier if you focus on dropping explosive gel all over. Tumble around and drop gel on the floor non stop, blowing it up until you notice that one Copperhead is dazed. That's the real one, so that's the one you want to punch in the head a bunch.
After a while the battle will change, and you'll need to mix dodging out of the way when she dashes towards you to your arsenal. It's not that difficult, because at this point you'll have been spending the entire battle tumbling around anyway. Continue until she's gone.
For more tactics here's our full Batman: Arkham Origins boss guide!