Change of work rota.

[Rainagainandagain]

Been in a new job six months, at a large supermarket. I've worked every weekend since I started. Next weekend I have Friday and Saturday off. Now my colleague wants me to swap so she can have the weekend off. I'm fairly new so don't want to upset anyone but need the weekend off to do Xmas shopping as in all Xmas week.
Feel awkward, don't want to be a doormat but kinda pressed to swap.
Any advice? Don't want to upset anyone.
I'm an older lady, family all grown up, so no young kids.

Just say “so sorry I have plans I can’t move”

If she pushes e.g what plans? Why can’t you move them”
Ignore the question and sympathise
“Yeah, sorry it’s a shame for you I can’t move them. Hope you get it sorted”

Then
“Mmmmm yeah, tough situation for you” on repeat to any other comments.

Agree with guardian and even add "normally I'd be happy to help, so feel free to ask in future, but this weekend is impossible for me'

Thanks for your reply

Good idea, thanks very much