[Maximo]

Sounds like she is sensitive and fearful of new things, especially "strange" and "restrictive" things that go on her body. Remember, none of this stuff is natural to a dog. Some dogs don't like when they see humans wearing "odd" objects like hats.

I would try introducing her to new items before putting them on her. First do something fun with her like play fetch, or whatever activity she likes. With a happy and confident demeanor, bring out the new item and say, "Oh, look what I got for my good girl!" Put the item on the floor and let her sniff, but not chew. Encourage her to check it out. In fact, use that phrase, "check it out." Give her small treats and praise for any movement toward or interaction with the new item.

Once the familiarity with the new item is established, then put it on her (harness, coat, whatever it is). Praise her as you do it. I think Yorkies love adoration. Tell her she is beautiful and such a good girl. Once the item is on, continue praising and distract her again with her favorite activities.

The more you expose her to new things, praise her for accepting new experiences, the more confident she will become.