She is a cutie-pie
Most yorkies will come in to season from 5 to 10 months old and will be classed as an adult from 6 months to a year, all toy breeds mature quicker than large breeds as some of them are not classed as a adult until they are 18 months old.
Of course it depends on what book you read as they all seem to say something different but generally dogs are classed as a adult when they come in to season if they are a female.
Most yorkie pups coats change colour from black to light silver or dark blue silver when they are adults.
Here is a pic of my tye and zac (dogs in the middle) who are about 6 months old in this photo and were about 4 pounds.
Tye has gone to rainbow bridge now but zac is now 17 years old and his weight is around 8 pounds so he still put on double his weight.
The first dog in the photo is tye and zac's dad who was about 9 pounds and the dog at the other end was there mum who was about 8 pounds so to be honest theres no real way of telling what size your little one will be.
My sasha also stayed the puppy black on her back and tye's coat still changed colour from black to dark silver to a mix of them both until he died when he was nearly 17 years old so theres no real way to tell that either.
The only thing i have noticed with the yorkies i have had over the 25 years is that there head and leg colour mainly stay the same after about 10 months old it may get a bit lighter or darker but none of them that have had tan legs then get cream legs and vice verser also all pups are born black and tan (apart from golden and such) but scampi and zac who later had light cream instead of tan were born with a couple of white hairs on there head.
Last photo is of sasha aged about 3 months and then one aged 10 months.