I'd say half a cup. A lot of people on Yorkietalk really love the Royal Canin. It's high quality from what I've heard. I'd feed half a cup -- you had it right! As far as her weight, that sounds okay for an 8 week pup ... she may end up around 6 or more lbs. To give you an idea of how much weight can vary, check out this thread:
http://www.yorkietalk.com/forums/sho...0618#post10618
Also, a puppy growth chart, used commonly for toy dogs, including chihuahua's:
http://members.cox.net/landrys_kenne...owth_chart.htm
As far as whether she's in the right
weight range for her
structure, ask your vet. The vet can ascertain whether she's just right or overweight ... or underweight for that matter. My pup was underweight -- 5 months, 3.5 lbs. But some people have full grown yorkies that are the right weight and weigh only 3-4 lbs.
Happy Gracie day! We can't wait to see pics!