You need your thread title amended to say “nanny”
Nanny and childminders are NOT the same - I’ve been both! Childminders have a LOT of regulation that Nanny’s don’t. It’s not just a case of preferred terminology they have meaning.
Either way your colleague is a cheeky fucker and I’d be telling her to sort her own childcare because her attitude will likely lose you your nanny!
No nmw is NOT acceptable in my opinion for the person you are charging with the care of your beloved children. That’s a hell of a responsibility and requires skills and aptitude’s beyond that of what’s required for many nmw jobs.
Also @mumwon is correct - legally if your nanny is caring for your colleagues child for more than 2 HOURS (someone said 3 it used to be 3 it’s now 2) in a place that ISN’T your colleagues home that THEN becomes childminding and the childminder has to LEGALLY be registered with ofsted (or with the care inspectorate in Scotland not sure about Northern Ireland) part of this includes the place where the care will take place being inspected for safety. This includes the childminder has to have a police background check (again called different things in different parts of Uk) and (again varies across Uk) but also is required to have public liability insurance, first aid certification, early years training, health & safety training, sometimes food hygiene certification
Your nanny working as a childminder for your colleague unofficially could land herself in a lot of trouble, which can lead to massive fines and I think your colleague can potentially land themselves in trouble too.
In these circumstances I wouldn’t presume that YOU would escape a possible fine too.
And frankly this colleague absolutely sounds the type that would sue if their child was injured/became unwell
Personally I think £18 ph for a VERY experienced nanny, caring for 3dc in a VERY flexible (for the parents) arrangement (ie she changes to suit you at short notice, happy to do extra etc) is a bloody steal!
Do not ruin that by facilitating your arsehole colleagues attempts to wheedle into that arrangement.
If her mother is really only going to be out of commission for Max 2 weeks then her and the children’s father can take annual leave to cover it! Them’s the breaks when you rely on family for childcare, pros and cons to all arrangements.
There’s also the worry of any surgical complications, extended recovery period etc. - I can’t help but wonder given the colleagues entitled attitude (such attitudes also tend to be passed on to children) if granny is looking for an Excuse to quit being childcare.
Again - not your problem!
A simple “no” really should suffice. But if it doesn’t point out to colleague that the arrangement she is suggesting is actually illegal and could potentially land all 3 of you in the shit with authorities (all it would take is a comment from a child to a teacher or other childcare person).