God gets mad at Sarah for doing what Abraham did?

Gen 18:10 says, “And he said, I will certainly return unto thee according to the time of life; and, lo, Sarah thy wife shall have a son. And Sarah heard it in the tent door, which was behind him.

18:11 Now Abraham and Sarah were old and well stricken in age; and it ceased to be with Sarah after the manner of women.

18:12 Therefore Sarah laughed within herself, saying, After I am waxed old shall I have pleasure, my lord being old also?

18:13 And the LORD said unto Abraham, Wherefore did Sarah laugh, saying, Shall I of a surety bear a child, which am old?”  Why is god questioning why Sarah laughed to herself?  Gen 17:17 says, “Then Abraham fell upon his face, and laughed, and said in his heart, Shall a child be born unto him that is an hundred years old? and shall Sarah, that is ninety years old, bear?”  Abraham literally fell on his face laughing.  God didn’t even question him.  Sarah only laughed to herself.  What is the big deal?  Is god sexist?