'She has replied saying she will be phoning me tomorrow evening. I can feel a tantrum coming on!'
Stop engaging with her and giving her a forum to behave like a child! Seriously. Just don't. There are many threads on here from people who have learned to free themselves from the bullying of toxic family.
She knows she can manipulate you on the phone or face-to-face, so don't let her! She has FA respect for you, you told her NO, her response is what you want doesn't matter shit to her.
You don't have to tell her what your plans are or what you're doing. It's not her business. You don't have to take her phone calls and listen to her. You can text her, 'I said no. There is nothing further to discuss. I will not listen to you carry on via the phone. I said no.'
She behaves like this because she's allowed to do so.
'If she is nasty about it , you should arrange to all do some helping at a homeless shelter or similar on Christmas Eve. 'We feel so lucky with our new house we had to do something for those with so little. We might see about making this part of our Christmas every year' it sounds right up her alley 😆'
Why should she compromise her life in any way or offer excuses or alternatives? She said NO. That has to be enough for a CF or they keep trying to rip the piss.
Get over to the Stately Homes threads and learn how to stop allowing FOG (Fear, Obligation, Guilt) from toxic relatives compromise your happiness and life.