Coco: I have a big mouth.

可可：我有一个大嘴巴。

You have a big mouth.

你有一张大大的嘴巴。

I have a big mouth!

其实我的嘴挺大的！

I'm not going to tell you the secret as you have a big mouth.

我不打算告诉你那个秘密，因为你嘴不严。

However, she is known to have a big mouth and she often spread secrets to colleagues.

然而，她有一张大嘴巴，常常在同事间传播机密。