Heaven has to be an illusion. If a Christian woman goes to Heaven, but her atheist son goes to Hell, then the woman is going to emotionally suffer, and it's not going to be a paradise for her. Since Heaven is typically described as a place without suffering, then that leaves three options:how would it be illusional? if all you are is a consciousness then only that has to be moved to a new eternal world which isnt hard for an infinitely powerful god.
1. Heaven isn't real (the mostly likely option and the simplest answer).
2. The woman thinks her son is there when he isn't, which would make it an illusion.
3. The woman is somehow altered to no longer care that her son is burning in Hell, which means she's a completely different person, and it's no longer the aforementioned woman who is in Heaven.