她小时候很淘气用英文怎么说

She was very naughty when she was small.
灵活一点也可以说：
She used to be a very naughty girl.

She was a naughty child. 或 She was a little imp as a child.
注意 naughty girl 口语里还有别的含义呢 (=indecent)！也不是孩子的意思了； ＋hoydenish 现在不用， 古代话

She was very nauthy when she was young
饿,竟然和2楼一样,不是我抄袭哦
可以,但是用young更好

She was very naughty when she was young.

she was hoydenish when she was a small child..
这样可以吗？

She was very naughty at an early age/in her childhood/when she was a little girl.