Karen has history in ice dancing so I presume she's their to judge the ice dancing. Bearing this in mind, let's compare her scores to the other skating judge on the panel for week one.

Robin
10.0:
9.5:
9.0
8.5:
8.0:
7.5:
7.0: Matt
6.5: Beth
6.0:
5.5:
5.0: Pamela
4.5: Samia
4.0: Keith, Shayne
3.5:
3.0:
2.4:
2.0:
1.5:
1.0:

Karen
10.0:
9.5:
9.0
8.5:
8.0:
7.5:
7.0: Matt
6.5: Beth
6.0: Pamela
5.5: Samia
5.0:
4.5: Keith, Shayne
4.0:
3.5:
3.0:
2.4:
2.0:
1.5:
1.0:

Albeit Karen scored higher than Robin she scored them in exactly the same order. So, for week one at least, while she may have been slightly kinder to all the skaters in terms of marks she was fair across the board (except her scores from top to bottom were closer than Robin's).

It's a shame Kati is gone but she comes from a long line of judges who just didn't hit it off with the British public. It's just one of those things.