I really do not understand how there is any point whatsoever in the defence attempting to use FB comments?! Those FB "friends" had never met Erin or her in-laws IRL, so why would their words count for anything ? Of course they are going to go along with EP, they only have her side of the story.
Jmo
I think this evidence, used by the defence, is not trying to show that her FB friends support her side of the story. I don't think the defence using this evidence has got anything to do with how she feels about her in-laws etc... Nor what her social media friends think.
They are using this evidence to show the context around the prosecution's evidence (which was trying to show Erin’s feelings towards her in-laws using a few social media posts from many months before the alleged poisonings).
The defence is essentially trying to show how frivolous the evidence is.