It's probably best to get them to structure it themselves though and then help them to improve that. If someone always tells you how to structure it, you won't learn to do it yourself. And, equally, when you give people a structure you prevent them from coming up with something better themselves.
I bet the teacher will be able to help your DD to recognise when she's waffling and to come up with her own strategies for structuring an essay effectively. It's the first essay in A-level so it doesn't need to be perfect at this stage. It should all be about development.
(If she wants a tip for an effective essay structure, the key is in figuring out what her argument is. Once she knows what the main point the essay is making, she can work out what points she needs to establish and in what order to make that argument effectively. It does help to be able to clearly state what your argument is in a sentence or two before you start writing. If nothing else, it helps to stop you waffling off topic. )