My sister washes her hands before meals否定句

My sister didn't wash her hands before meals

是否定句还是否定形式？
否定句：My sister doesn't washes her hands before meals.
否定形式：My sister doesn't have washes meals until she washes her hands.

My sister doesn't wash her hands before meals .对

My sister didn't wash her hands before meals. 错，第三人称阿，老大！

My sister doesn't wash her hands before meals

我妹吃饭前总要洗手。