Thanks I'll try the alternate word (and suggest it to mum too)...maybe 'fiddlesticks' or something similar and a bit funny (other suggestions gratefully received).
The swear box wouldn't work as she doesn't bring toys etc from home and we tried the sticker chart to no effect.
We're using time out at the moment, it works for a while, but a few hours dowm the line or the next day it's forgotten. Some days she seems to be in and out of time out, so you kind of wonder if it's counter-productive.
I've observed her and noted the times when the swearing is most prevelent - it's those times when you can't give her the attention she wants like when you're serving dinner or you're on the phone. I've tried numerous ways of distracting her but you can't do it 100% of the time and she seems to wait just for those moments before letting off a tirade of expletives.
I'll get my thinking cap on about a rhyme.
Do you know of any books? I've got various childcare ones like toddler taming, discipline without smacking or shouting etc
Thankfully the teenage sibling has been dealt with.

Any more brilliant suggestions out there?
thanks