Now fast forward a few years to when she essentially feels like her parents were divorced. Or her siblings barely know their mother (heck, even at 5-years-old the daughter barely knows her) - what kind of a presence will Miranda be in their lives? These aren't just rhetorical questions - they're questions the character should be asking herself.
Who's to say that these questions won't be addressed as the series goes forward? It strikes me that the character of Miranda was introduced with probably these very issues in mind.