@QueenofmyPrinces
*I can see why she would be hurt and angry that this was allowed to happen.
And you think this level of anger is normal 4 months later? To the point of talking about damaged relationships and needing to protect her children from MIL?*
Well, in my experience when you don't acknowledge an issue, tell someone that their feelings aren't really important and that they should move on, that is exactly the opposite of what usually happens. Instead, the hurt and anger continues to fester. So I am not entirely surprised that OP has not "just got over it because her DH wanted his mum there, so it's fine".
I think that had it been acknowledged that what happened was upsetting for OP and against her expressed wishes, and therefor should not have happened, it is more likely that OP would not be so hung up on this particular issue. I also suspect that this incident is just a concrete example of how she feels that he feelings aren't really listened to. I wonder if OP fears her MIL imposing her wishes/thoughts/feelings on other matters and that her DH will not oppose his mother? I am not saying that IS the case, or even that her DH would do that- I simply don't know- but I wonder if that is what OP fears and why she is wanting to "protect" herself and her children from MIL.
It may not be rational from your point of view, but when your wishes have been ridden over roughshod at a time when you are most vulnerable, it can make that feeling of vulnerability more profound. Worse, it can make the though of being in a vulnerable position more frightening- because now there is the fear that what you want will be ignored again if you aren't in the position to make sure they are respected. If you are already wary of letting others see your vulnerability, as OP has said, this is more likely to confirm that you were right than show that it is ok to let others in.
To have that happen to someone whilst they were unwell, recovering from a major operation and waking up with no idea what the outcome had been for your babies and whilst most likely in pain and confused- i.e. when you are at your most vulnerable- is an upsetting thing. I say it again- in no other medical situation would this have been countenanced as 100% fine. Some people may choose to take the view that as OP's DH was getting support from his mum OP should just suck it up, but I don't think that's fair.
Although I do think it likely that MIL was worried about her son and wanted to be there to support him, which is totally reasonable, and was simply thoughtless and being a bit bossy/matriarchal rather than malicious (unless she has form for the latter). OPs DH is really at fault here as he did know what OP wanted to happen, yet did nothing about it. He could easily have asked his mum to wait outside until OP felt ready to see her, and she could still have provided support to him.
As it happens, I think OP does need some help to come to terms with the really tough time she's had. With that, she may be able to let go of her anger (not because she is not entitled to that anger but because it is going to cause her more damage than anyone else) and find a more positive way forward. None of that changes the fact that what happened wasn't fair, at a time when OP felt vulnerable.