Now, three months pregnant, does she have a moral obligation to make her new employer aware?
Yes, she does have a moral obligation to inform them. It is only right that she give them a heads up so that they have ample time to plan for her impending maternity leave. If she is worried about the prospective employer rescinding an offer, they have no legal leg to stand on, so I doubt this would happen. Her best bet is to be up front with them. But I can understand why she is reluctant to tell them–finding a way to cover her workload while she is out will be an inconvenience that they had not planned for and there is obviously some risk that she will not want to return after the baby is born.
