I don’t think it even should be about proving individual women are vulnerable to anything in particular.
The point is that collectively female prisoners should be guaranteed single sex housing. We don’t need to justify that by finding counter examples of vulnerable individual women or whatever. it should simply be a fundamental right for all women that, should they be imprisoned by the state, they will be housed in single sex prisons.
Biological men, however they identify, will be housed in the male estate. If trans inmates are unsafe in the male estate, then changes should be made to the male estate to keep them safe.