From the tower in the SW of the Vale, cross the road to the south. Kill the 3 young grendalorms that spawn together for a long time and she will appear.
She was orange to me at 8th, and at 9th she was...orange, thus annoying me greatly. So I would guess she varies between 9th and 10th at least.
Since I cant kill oranges, I have not got her yet. Does she drop anything? Is she part of a quest?