She can. Kiru is quite large- there's plenty of places Niki can attack.

Yeah. So she attacks her in those places. Without hurting herself.

She soon discovers that Kiru can't -easily- attack her if Niki goes for her legs, near the knees. Kiru's legs are a bit short, and hence not long enough for her to attack Niki with.

Good. She attacks her legs.

She soon notices that Kiru's front left leg is the one she uses the most.

Then she attacks that one specifically.

For the most part, Kiru just ignores Niki. Her focus is on Furna, the one who isn't afraid to get himself hurt.

Well that's good for Niki. Not for Furna.

For a while, Kiru seems to be actually fighting. Then, she eventually gets tired of that, and smacks Furna across the head, stunning him enough to stop, but not enough to knock him out.

Wow.