This is how controlling, coersive, abusive relationships go unnoticed.
'It's just a cake, you're being ridiculous'
'Great, two cakes, whats the problem'.
It isn't about the cake is it?
What if its:
'I asked you not to give my child xyz food they are allergic to, but you did it anyway as you think you know best'.
'I told you there was no need to give X their dose of Y, because I had already given it today'.
'Please don't give child X because we've already discussed it and they are not allowed X at present/at all/ever for reasons important to us'.
Or other relationships:
'Please don't bring me extra calories, I am sticking to a diet'
'I've already said no to a date...'
'I have already said no to sex...'
Whilst a Grandma bringing cake they were told not to bring is unlikely to result in rape, (hopefully!), its modelling 'this behaviour is OK, doing things people have said they do not want, do not consent to, are not happy with, is ok if you dress it up as 'being nice'.
This is how we get young boys told its FINE to persue a girl even though she's said no repeatedly because 'they're being nice'...
It is teaching (mostly women!) that you have to accept and 'be nice' about things you've already said you don't want, aren't interested in, solutions to problems you've already resolved... because otherwise you're being ridiculous, over sensitive, silly, dramatic... etc.