I would immediately start making a much bigger fuss about this. I am extremely angry on your behalf and would expect the university to be doing much much more.
If your dd is disabled with IBS and because she is female, they are essentially bullying her both in person and online. Online bullying is a CRIME and I would be writing a letter today, cc'd not just to the Deanery but also the Vice-Chancellor's office, the housing office, the welfare office, explaining your dd is being victimized and harrassed online and has the emails to prove it. She won't be attending a mediation session as she is intimidated and scared and the onus on the university is to keep her safe and to protect her from discriminatory bullying (which it undoubtedly is as she's female, has IBS ).
This is as bad as the Warwick case IMO and should be setting off alarm bells in any university right now.
I would also say in the letter that your dd (if she agrees) fully consents to you, her parents, being cc'd into any further correspondence (she has to agree to this and explicitly state it).
I would also state that I was taking legal advice on how to proceed with both the cyber-bullying and the harassment, and I would really do it.
These men don't just need removing from the hall, they need disciplining beyond that, in terms of their academic studies.
Escalate this above the deanery, this isn't a housing matter, it's about how females are allowed to be treated at this university. This culture of dominant nasty male entitled behaviour has to be stopped in its tracks and the perpetrators need to know that if they behave like this, it will jeopardise their careers and their uni records, not just get a slapped wrist and a nice mediation session in which three of them gang up against one. Go to the very very top (VC).
You could also threaten to go to the media as well that's your call.
Good luck.