A spray tan is definately the way to go, I would advise that your daughter go to a salon to get it professionaly applied rather than try to do it herself. Some of the new spray tans look very natural from the word go and they can even shade certain parts of your body to make you look slimmer!
Regardless of the make of tan, I have tried St Tropez, Fake Bake and other spray tans, they all have that chemical smell and do leave a residue on your clothes regardless. The salon will probably recommend your daughter to wear loose clothing, a dress or skirt is better than trousers and also light shoes, even flip flops if possible.
As others have said the tan will last about a week, but your daughter will be able to top it up herself quite easily if she buys a good quality spray tan, like St Tropez, she will already have a good base colour, so anything she puts on top should not go streaky. I used to do this, but I would never wait until the original tan was nearly off, but used to apply any top up day 4 or 5 into the tan.
Hope this further info has helped, best wishes to your daughter, I bet she will have a lovely day!
Sue