My first take is that her husband is threatening to leave her if they don't have kids soon. She doesn't want kids but doesn't want to tell her husband that, so she's faking it so he will get off her case but still stick around.
My second take is that one of her friends is pregnant and she wants to be too but can't get preganant, so she's trying to keep up with the Joneses by pretending to be... she will get all the same attention and then the sympathy too when she suddenly very suspiciously miscarries.

Whatever the reason... she's nuts.
