I have never heard of her... which as a rule of thumb I think is about the right response people should be having. Much as I love Capaldi (best Dr since 1983), I do dislike how the show sometimes feels like a vehicle for people who are already famous, whereas I like it when they give chances to hitherto unknown/under-appreciated talent.
Have ABers seen this woman in other stuff? Is she actually quite well known or is it just me who's never heard of her.