I would be afraid to use advantix again. My maltese hade a reaction to it. I use frontline on both of mine but I split the dose between my 2 dogs. She may also just be under stress. You might want to look at Missing Link to help build her health back up. It’s supplement, could help her with her hair loss. Read the testimonial page on the supplement and ask your vet about it.
http://www.designinghealth.com/testi...stimonial.html
Don't know what type brush you use but maybe you could try a different type brush. If she was abashed they may have hit her with a brush or something that resembles a brush in size. Try a Denman hair brush, they grip the hair and glide thru, doesn't pull the hair or hurt, my dogs love them. They feel really good to use and are really marketed for humans. You can buy them at some hair salons, beauty supplies or online. I first heard about them on another yorkie forum a few years ago I use a D81
http://www.denman-us.com/Denmanbrush/Cushion.htm
As far as brushing her teeth my vet recommended taking a piece of panty hose and wrap it around the tip of your finger, apply doggie tooth paste & polish their teeth. It's really hard to get some dogs to accept a tooth brush, the tiny ones have such small mouths you may have more look using your finger.
I believe isofluorane is the anesthesia thats suppose to be safer. There's another member on here whom 2 tiny yorkies & also has her own website with lots of info on tiny yorkies and health care
http://www.mylittlemia.com/ . She may be able to help you with vet info or what to ask about concerning their health and spaying.
Sounds like she needs some TLC. good luck with her.