I'm ok, just exhausted. Had to explain to DP that I wouldn't choose our future children's birthday cake, I wouldn't dictate which decor they wanted for their parties, how silly of me to say white cake is more delicious than whichever flavour they happen to like.
He has apologised, but he is adamant he wants to stay out of it. He likes my mum too much-and doesn't want to be a part of this, even privately siding with me. 
He doesn't think picking a yearly bday cake is same as seeing your child start a family of their own, but he said he understands that I want to be independent of mum, yet he also understands her feeling like she's losing me.
What is mum so sad about? I'm not moving to another country.
Dad is being being quite as well and acting like nothing is happening. He's been stressed about coronavirus and doesn't really want any more added stress- and I think DP is feeling the same way.
Thank you all for the suggestions! I am happy, healthy and looking forward to a lovely small celebration
full of now 'David Austen roses'
per mum.