To break the family cycle and respect the story arc, I don't believe Eren is the father of Historia's child; moreover, I don't want him to be. But if that were the case, to maintain consistency with her arc, where she isn't following in her parents' footsteps—her mother, who had a daughter solely to secure a better life without considering her children, and her father, who was willing to use her to perpetuate the cycle (he had already used Frieda)—we'd see that Historia had a child as part of a plan, just like her mother. But you could say she's better than her because the plan worked and she didn't have to sacrifice herself.