Hello and welcome!
8 weeks old is VERY young to be bringing home such a wee one - and unfortunately, you're learning the hard way. Yorkies are VERY prone to hypoglycemia as pups, so please buy some Nutrical from Petsmart or somewhere and give it as soon as she shows signs of lethargy or low blood sugar.
If she is waking up w/ low blood sugar, you may want to give a bit before sleep and as soon as you/she wakes up, to avoid the nausea and all the other symptoms that go w/ it. You should feed her about every 4 hours until she seems to grow more stable (poss. until she is 3-4 mths old) w/ her sugar levels.
Hope she is feeling better today, please keep us updated!