Red squigg's tweets are horrible, and I am sure it would be very upsetting to read something like this about yourself.
But Jack said "a conversation today where the people behind the accounts were speculating on how far and how exactly they would need to push me and my mental fragility before I killed myself". If this is the conversation she's referring to, then that is a misreading (wilful or otherwise).
Black squigg is saying we can never know what state someone is in, so be careful with your comments.
Red squigg is deeply unpleasant, imo, but they are saying they don't believe Jack is vulnerable, so he/she feels it is acceptable to keep pushing Jack regarding certain topics.
I'm not defending it, but Jack has misrepresented the conversation, in my opinion. Perhaps she is referring to a different conversation.