@PeregrineTook That "little redheaded girl" is Laura Zanna, the twin sister of the Gen3 vampire heir, Vitoria Zanna. On her teen birthday, Laura becomes a vampire, too. No doubt she will be a knockout, too.
With all three Gen4 spouses decided, Jagger and Alfonso are really just "vanity spares," lol. I guess it depends on whether or not Laura takes the vampire cure and becomes the Gen4 painter...
About the red and green Character Value bars, a full green bar like Responsibility gives an associated positive trait at the next birthday (I think it's the next birthday not the YA birthday).
A full red bar results in the Uncontrolled Emotions trait, whereas a full green one turns into the Emotional Control trait. All the info can be found in Carl's Guide.
I still haven't tried the teenager aspect of the Parenthood GP but, really, the heir's the only child whose upbringing matters, so I can just experiment with the twins.
Funny thing is, I worked (my sims) really hard at Parenting in my other story with negligible results. It's much easier this second time with fewer children.
I think you would enjoy the various Advice chance cards.
An IDC is a better vehicle for playing the Parenthood GP, imho. In my RDC, everything moves too quickly to really observe how the new mechanics influence child development.