I think she knew about the clown video because she raised an objection about it being shown in court. It was her or someone on HKS's team of lawyers that raised that objection. But of course the judge said "you got to show your, so they get to show theirs". How stupid IS this woman???
THAT opened the door for Seidlin to include the clown video. But then Barth thought she had him on her side then, and she thought he would exclude the clown video.