I'll just c/p what I did on FB here, and again say how sorry I am. That's really sucky.
I'm so sorry. DEFINITELY harness. I know some think CT is not a big deal, but in some breeds, especially the little guys, it really can be. I know of a lot of yorkies who live great lives with CT, but could have been prevented by wearing a harness to begin with. But many things can lead to CT... Obesity, inhalation of irritants or allergens, respiratory infection, enlarged heart, etc.
As I'm sure you already do, just keeping her leaner will help. Harnessess instead of collars, humidifying the air, etc. I have a friend who has a bigger yorkie, Jackson's size who has it. I can ask her some questions if you want, but she seems to live a super normal happy life.
Try to avoid lots of stress, overly excited (I know, easier said than done with Mia). I've read cough suppressants can be used to reduce irriation to the trachea. I think u do have to be more cautious when going under as well because of the tube. So glad you were in tune to her and brought her in!
I did ask my friend with the yorkie and she said her moms yorkie has it worse than hers and is on a medicine for it daily. I will get the name of the medicine for you tomorrow. She said it helps him a lot. They also both love Buddy Belt harness, no pressure on neck whatsoever.