The issue is she's not taking no for an answer
No - the issue is that you want her to happily take no for an answer and are trying to coax her or persuade her to do so because you can't deal with the emotions she's displaying.
In order for her to take no for an answer, all you have to do is keep saying no. The event will pass and she won't have gone to it.
On a daily basis, however, you take care of the pets and do the chores. This is because you are afraid of her feelings.
Because you're afraid of her feelings, or unable to cope with seeing her sad/ angry/ performing misery, and because your husband can't cope with arguments/ raised voices (or whatever) you've given your child the idea that her feelings are something big and scary, and not something that she can be aware of and come out the other end of.
This is the opposite of co-regulation. Co-regulation involves sitting (in a broad sense, not necessarily right there on the couch beside them) calmly with the child and letting them know you understand they are sad/ mad/ frustrated BUT you are not going to change your mind regardless of the noise they are making and regardless of how heartfelt the emotions may be. The aim is to teach the child that feelings come and feelings go, but once they've washed over you, you can re-enter your life, and take up where you've left off.
You do not co-regulate by persuading the child to be happy. That bit is completely up to the child.
All you have to do is let them know you understand they have deep feelings. Then you let them know that you expect them to get over those feelings, and that this is desirable. You let them manage this part themselves. If they persist in throwing a tantrum or winding themselves up, you are allowed to tell them you hope and believe that they'll soon feel better, and get on with your own life.
You do not need to hover or explain or engage in any more soothing.