"My mother is preparing to cook" 或者 "My mother is getting ready to cook" 可以用来表示你妈妈正在准备做饭。

来源：这是一句简单的英语句子，由主语（My mother），谓语（is preparing/is getting ready）和宾语（to cook）组成。

例句：

"My mother is preparing a depcious dinner for us tonight." (我妈妈正在为我们今晚做一顿美味的晚餐。)
"I can smell something depcious, my mother must be getting ready to cook" (我能闻到一股美味的味道，我妈妈一定是在准备做饭)