She says her stomach hurts and school starts Monday.

There's nothing wrong with her stomach. You know that, and telling her so hasn't helped, because she isn't lying — it genuinely hurts. Meanwhile everyone keeps saying “you'll love it!” in a bright voice, which she has correctly identified as the voice adults use when something is going to happen whether she likes it or not.

What actually helps

• Believe the stomach ache out loud. “Your tummy really does hurt. That happens when something feels big.” Naming it as real, and as a feeling rather than an illness, does more than reassurance does.
• Stop promising she'll love it. She has no evidence for that and it makes you sound unreliable. “Some of it you'll like and some of it will be boring, and I'll be there at the end” is a promise you can actually keep.
• Get concrete about the shape of the day. Most of the fear isn't school, it's not knowing the order of things. Where I hang my bag. Where the toilet is. Who I sit with. When I eat. Who comes to get me. Walk it through until it's boring.
• Answer the real question early. The real question is almost always “who is coming back for me, and when.” Say the name and the moment: “I'll be at the blue gate after story time.”
• Make the goodbye short and identical every time. Same words, same hug, same exit. Lingering reads as “this is dangerous enough that I don't want to leave either.”
• Don't debrief on the walk home. She's spent. The answers come at bath time or in the car three days later, when you've stopped asking.

Why a book helps here, when talking doesn't

You can only walk her through the first day so many times before she stops listening. A book she can open herself, at seven in the morning while you're finding shoes, does the same rehearsal without you having to run it — and she can do it eleven times without anyone getting tired of the question.

A book about her school. Not a school.

Her name, her bag, her teacher's name if you know it, the friend who's going too, the exact gate you'll be standing at.

Written the way that works: the nervous bit is in there and is allowed to stay nervous, nothing magically becomes fun on page three, and she comes home at the end.

Or the whole book in outline, for her to color.

You choose how it's drawn: painted and full color to read tonight, or the same story in plain outline for her to color herself.

The week before school starts is long. Coloring the classroom in her own colors is a way of making it hers before she's ever stood in it.