What book that I read as a child in the early 80's contains a garden of statues

Question:

What book that I read as a child in the early 80's contains a garden of statues who come to life at night?

I remember the main character as being a girl who is transformed into a statue too by magic and at one point in the book she swims across a lake to some sort of temple where the statues gather... There's a boy in it too who's also transformed.

Best Answer - Chosen by Asker: "The Enchanted Castle" by E Nesbitt?
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"Draughty," said Eliza, "and law, what a lot of steps to clean! What they make houses for without no walls to 'em? Who'd live in," She broke off, stared, and added: "What's that?"

"What?"

"That white thing coming down the steps. Why, it's a young man in statooary."

"The statues do come alive here, after sunset," said Gerald in very matter-of-fact tones.

"I see they do." Eliza did not seem at all surprised or alarmed. "There's another of 'em. Look at them little wings to his feet like pigeons."

"I expect that's Mercury," said Gerald.

"It's 'Hermes' under the statue that's got wings on its feet, said Mabel, "but "