It seems to me that Connie's Liography might have a clue as to why this is. Let's scan through this passage to see what might be the problem:
Love may have come easily, but their families' acceptance did not. Lawrence was understandably wary of yet another man intruding into his and his mother's life, and Greg's two teenage daughters, Molly and Gayle, were downright hostile about the prospect of someone taking their mother's place.
Greg approached the problem with his own quiet brand of diplomacy. He brought them all together for Thanksgiving and, with the children present, gave Connie a "friendship" ring. Not as shocking as an engagement ring, it still made the point clear that he and Connie were together. They were all going to be one big, hopefully happy, family. The kids would just have to deal with it.
By Christmas, Connie had run out of patience, waiting for Greg's daughters to deal. Always eager to move on a decision once she had made it, she hated hanging in limbo. While the two months since Thanksgiving had helped to warm the relationship between Lawrence and Greg, Molly and Gayle seemed to be getting more negative toward Connie. She suspected the girls thought they could delay the wedding forever if they acted out enough. It was time for decisive action.
The decisive action that she took was proposing to him. Since he didn't want to wait either, the die was cast and they were married before anyone could react to it. Let's scan down through the page to gleam more wisdom:
A month later, he told her he was being transferred to the bank in Milborough. He never admitted it, but she was certain he had pulled strings to get this particular transfer.
She and Lawrence were thrilled with the news of the move. Molly and Gayle were horrified. They had lived in Thunder Bay six years and had established a circle of friends there. Molly had a boyfriend. Her father couldn't stand him, which made her certain that the move was a deliberate attempt to split them up. She was partly right.
"She's getting in with a crowd that worries me, Connie. And wherever Molly goes, Gayle tags along. I think this move might be the best thing for them, too."
With grim persistence, the girls made their unhappiness all too clear.
Curiouser and curiouser. Let's see a little bit more, eh?:
Despite the girls' determined efforts to make everyone in the family as miserable as they were, there was more pleasure than pain for Connie in the move back to Milborough. Part of her happiness lay in finding a house beside Elly and John's. Their long-time neighbour, Mrs. Baird, was moving to a senior's residence. Although her house needed work, it had a wonderful garden and was large enough for the whole blended family. Besides, Connie had a strong hunch she would need a friend close by to talk with as she struggled to earn her way out of her assigned role of wicked stepmother.
By the time Molly finished high school two years later, the family had settled into a degree of peace. Molly still clung to her resentment, but it had become more reflex than real. She and Lawrence had become surprisingly close, in a teasing brother-and-sisterly way. The casual warmth of their relationship seemed to take the bitterest edge off Molly's attitude. Gayle's temperament was more easy-going, and Connie felt she might have been happy in her new home if it hadn't been for her older sister's influence. But when Molly graduated and entered college, Gayle decided to leave too, to live with her mother while she finished her last two years of high school.
Hmm. What this tells me is that Molly and Gayle learned a hard lesson: "Speak your mind but don't expect to be listened to." What Connie calls being assigned the role of wicked stepmother is what I call a logical reaction to dealing with an irrational, selfish jackass who thinks that the world owes her a living because she fails at everything. I should think that the reason that they get along as well as they do in the here-and-now is that Molly and Gayle finally realized that Daddy set the poor, dumb woman he married up to take the hit for his jackassery.