AC-12 here. In one of the interviews publicising the Radio 4 programme, SH said that 'Becky' had apparently said that the only reason she could think of to explain why she had made mean comments here was because SH looked like a friend of hers with whom she was having difficulty.
The Mumsnet poster seems to have extrapolated from that to conclude that we are all having difficulty with someone we know who looks like SH. Or maybe it's that we all know, and are all having difficulty with, Becky's friend who looks like SH.