Giselle mentions to Morgan in the first film that she has met many wonderful and kind stepmothers back in her own world. This proves that stepmothers are not evil and abusive by default even in fairy tale settings like Andalasia, so at first it may seem odd that Giselle is being forcefully changed into a stereotypical Wicked Stepmother in this fairy tale reality of her own making. Until you remember that Giselle made her wish right after an argument with Morgan, during which Morgan made a point to say that Giselle was ruining her life and would never be her real mother. Giselle's spell was changing her into a cruel and selfish stepparent because she believed that Morgan already saw her that way, when in fact Morgan just said that out of anger and frustration and actually wishes that Giselle actually was her real mom.
It seemed unusual to cast Broadway veteran Idina Menzel as a supporting actress in a musical with the first film and not give her a chance to sing. But then she gets to sing two songs in this sequel, after she's moved to Andalasia — a place where bursting into song is much more common than the world Nancy's from. Although this could be argued to just be an Author's Saving Throw, especially considering her rise to Disney music royalty as Queen Elsa with "Let it Go".
Mixed with Fridge Tearjerker. Edward sending Nancy to the real world alone while he stays to protect Andalasia may have been him saving her from dying alongside Andalasia, as he very nearly did.
Morgan growing up into a Deadpan Snarker makes sense when one knows that children's future personalities tend to start forming in the first three years of life and is influenced by those around them, primarily caretakers. Who was Morgan's only caretaker as a toddler? Her father, a notable Deadpan Snarker.
Consider how young Morgan was in the first film (around six years old) and that Robert had been dating Nancy for five years, since Morgan was about one. All this heavily implies Robert's ex-wife and Morgan's biological mom abandoned them when Morgan was less than a year old. Now that Morgan is a teenager, she may have only now realized her biological mother abandoned her. Part of her lashing out could stem from abandonment issues, feeling like she's losing another mom, due to not being Andalasian by blood like her sister, and thus seemingly incapable of joining in on the magical whimsy that Giselle represents.
Andalasia dying leads to Giselle (briefly) dying. What could it have done to half-Andalasian Sofia? If Morgan hadn't wished herself home in time, in addition to losing her mom, Morgan could've lost her beloved baby sister.
Consider the damage a grown woman like Giselle was able to with the reality warping wand, and remember that Edward and Nancy intended it to be used by a child.
