Need help please

I know this girl she is trying to get pregnant with this guy. But she told him that she can never have kids because of her age plus she is 45 years old almost 46 so there having unprotected sex right now she is hope to get pregnant next month. But she doesn’t want the guy to know and when she does get pregnant she is going to dump he’s ass because she know that he is seeing other girls behind her back. I know this guy and yes she is right he is seeing other girls. But shouldn’t he know that she will be pregnant with his kid? Do u think it’s right that she’s not going to tell him?