-
Unfortunately for Claire Williams, the slump started when she took over.
Claire Williams was appointed deputy principal in early 2013. For the five years previously, Williams had finished 8th, 7th, 5th, 9th and 8th in the constructor's championship. While they finished 9th in 2013, they finished 3rd in 2014 and 2015 after her appointment, their best results for over 10 years, and 5th in 2016 and 2017. I don't think the data supports your assertion.
Unfortunately for Claire Williams, the slump started when she took over. I honestly don't think it was her fault particularly but there's been some odd decisions and the fact they've done the worst of any Mercedes engined team in modern F1 means that this was pretty inevitable. I think she was still only Deputy Team Principal which probably indicated that there was something a bit dysfunctional.
You've got to say though, unless the new owners attract some design talent and pour money in (or do a Racing Point), they're not going to do any better.