I apologize. I could have been more clear.
I agree with telling him what she plans to tell him in regards to being safe in planning a scene. NOBODY wants to be involved in a scene gone wrong. I've stated that above.
Staying silent when something could hurt someone isn't my style.
I meant in her OWN emotional management -- where she feels it is "too harsh" to tell him "No, I'm not willing to attend."
I think she could let that feeling be what it will be -- let it
be "it feels too harsh to say no" but tell him she doesn't want to attend anyway.
Say "no" because that is where her actual willingness lies. Not say "yes" just because "he asked me nicely for once."
The OP seems to struggle with saying "no" so the first few times she does it? It will likely feel UGH. Could let it. As she gets more practice with it over time, it will hopefully feel less yucky and easier to do. "No" doesn't have to be "mean." It can be said firmly but kindly. And sometimes it is necessary.