@Tringley "Tbh, I'm not sure what you can get out of this thread. You could be 100% right you could be over-reacting. We can't know and it's impossible to advise you."
That is not true at all. A lot of people have advised the op.
Also several people have told the OP they have been in similar circumstances and others did not believe them, e.g. above your post
@Andro said (I am so sorry for you Andro) replying to "Interesting that the people you have told about the incident seem to think you are unreasonable -
That doesn't surprise me! I have 2 siblings who have endangered my life deliberately (to the point of putting me in ICU) more than once, I refuse to have them in my house (or near my dc without a trusted adult present) and my mother thinks I'm I'm being hysterical/unreasonable/overreacting."
So what that tells the OP is that even if she did spill the beans (against her better judgment) and tell us all whatever happened some would still say she needs to move on, put it behind her, what about the funerals of the future etc etc.....
"It's why the advice you are getting is all over the place with people supporting you and others calling you overly-dramatic."
No that would be because some people feel family ties should be preserved no matter what!
"Your posts do come across as incredibly dramatic which might be completely justified but it mightn't be. The information you have given isn't enough for this thread to do you any good."
Let's assume as Mumsnet suggests that OP is telling the truth. And this is a really serious thing.
The OP is not asking if to decide if it is a really serious thing or not, she is asking for advice and support about the wedding. And she is getting it regardless of whether we know all the ins and outs of whatever happened.