While a 10 year old may not be too fussy about strings (aside from attractive color options!), you might expect just a little trial and error to get the right tension for her. Maybe not - it could certainly come out fine for her the first time.
That string type is great for your young "slug-ette" (I prefer 16 ga. syn. gut in my racquets) and the first stringing you have done will give you a reference tension. If you ask to have it done right at mid recommended tension or maybe one or two lbs. higher, then you'll know what to do in case it feels awful for her.
If the racquet feels like a rubbery disconnected marshmallow when she hits the ball, restring 2 or 3 lbs. higher. If it feels harsh, like hitting the ball with a strip of plywood, try restringing a couple lbs. looser. Also be careful to not change too much at once - this applies to all of us.
If let's say you want a softer setup and decide to switch to a softer type of string like a multifiber, you probably want to go with about the same tension that you used in the previous setup, just so that the change isn't too unpredictable.