Lazy saying at the end that Isla wants to be the middle child so that she will 'be with Esme'... this is going to end in tears.
I can't help but worry she thinks that she and Esme have grown apart because they always used to be the littlest, but now there are four of them, they're divided into Isabelle and Esme as the biggest and Isla and Jace as the littlest. To a nine year old, that probably explains why her sister she used to play with all the time now prefers spending time with Isabelle, and she's always lumbered with Jace. The new baby can now go with Jace, and her and Esme's closeness is restored again, because they're both the middle children.
If that's why she's so eager to be the middle child so she's with Esme, Lazy and Creepy need to explain to her life doesn't work like that. The poor child is literally going to be right in the middle- too young for her older sisters to want to join in, but too old to play with the two little ones. It's only going to get worse.