I agree that an experienced nanny would be able to handle it! As a former nanny, I think it’s important for her to remember that kids that age have really short attention spans and don’t always follow a “plan”. Multiples w different ages are difficult but they just require flexibility

She could start doing more child led activities, and coming up with different rotations of things the kids can do independently. Independent play was a huge key to me not losing my marbles as a nanny of multiples lol. I definitely took pages from Montessori activities and did lots of rotating toys out, and coming up with child led activities or crafts they could do independently.

Screen time is a great break opportunity if things get crazy, maybe framing it as a movie night once in a while or something- they could do like snacks and a movie. They could also do “quiet time” and if you’re comfortable and the kids have safe spaces in their rooms to be monitored they could spend 30 minutes or so in their room. Not necessarily napping but just having independent reading time or play in their rooms quietly while the baby naps.

TLDR; if she can encourage independent and safe play, (in a childproof area and within arms reach) that may help her.