Weight is most important.
My daughter ( 7 yrs old and 75 lbs at start of season) skied well on a moderate side-cut Dynastar Speed 8 jr @ 130 cm in her first race season.
The Dynastar 10 jr (no plate) is an option since it's the next step up. But, the radical sidecut maybe better suited to when she is around 9-10 yrs old and stronger. She may simply be on a longer 8 next year.
At 4'7" and nearing 80 pounds, she needs to add 20 pounds or more for powerful skis. Plated skis are out for that reason. They will have to wait until she is 10 or more.
My choice is between an unplated 10, and a longer 8. A lot will depend on her weight at the start of the season. Ability and athleticism do play a part, but the bottom line is that the young racer must be able to flex the ski.
So, are they heavy enough? Are they aggressive enough? Are they skilled enough, ie, are they always parallel and out of the back seat? Yes to all, and you can take one step up -- but not to the top model at the age of 8.
Beware that at the age of 8 only exceptional athletes are fully parallel and not in the back seat. A radical sidecut and too stiff a ski will put most kids further back.
You may wish to consult a growth chart to help estimate your childs height and weight next year.