Well, we just returned from the vet. We treated her for fleas when we brought her home but the vet said even a couple fleas could cause problems in such a small dog.
So, we're starting with the assumption of flea dermatitus (probably spelled that wrong) and possibly a flea allergy. She gave her an antibiotic and omega 3 fatty acid vitamins. We're also rubbing her coat with a Tea Tree Oil that's supposed to sooth the skin from any irritations from flea bites.
We go back in 3 weeks and see what progress has been made. Then she'll look at some other tests if things haven't improved. Hopefully that will be it. Otherwise, she's in great health.
Lexi is so precious. We fell in love with her the moment we saw her, whether or not her coat is full, she's become the baby of the family!
Thanks again for everyone's comments. What a great group of people