Hiya Michelle,
I glad that your Sophia has got through her illness. Well done to you.
It's not a set rule the weight of a dog. She's still a baby and growing. There are the ideal height sizes for schnauzers but they don't all come out of the same mould.
The best way to tell if your dog is the correct weight is to place your hands either side of her shoulder blades, then gently move them down her body accross her chest. Your feeling for her ribs, and you should be able to feel the bones. You don't want to be able to see the bones, but you want to be able to feel them without putting too much pressure on the dog.
I have four mini's and my boy is far too tall. When feeding them I try to sick to the recommended amount of food, but Monty always needs more, because he is larger. Are you going to training classes? They are great fun, and mini's are very clever. I've just started agility with one of mine. She loves it and I'm keeping fit.
Nice talking to you.
Jane.