Kids don't always react well to having siblings, be it from a blended family or simply a younger sibling with the same set of parents. I never saw Riley in tears, but maybe you have means we don't? I didn't see her acting like she didn't like AJ's children, she said they would be "friends" not brothers or sisters. That indicates that she doesn't want to share her mama. Understandable, especially for a child her age who's an only child of a single mother, but not indicative of an unhealthy relationship. Any change is going to put stress on a child, but if it's going to be stress with no real positive outcome, then that's a bad thing. But Riley was going to gain a father figure she clearly adored, and brothers and sisters that she clearly liked. The only "stress" she was dealing with was sharing her mother. It's hard, and it's painful, but frankly, it's just something that happens.