Why does my dog get mad when I sniff her 😅

I have the Goodest border collie blue heeler mix. She was rescued from a cattle farm after being abandoned by the owners. The neighboring farm took her in, but she relentlessly chased their single dairy cow until it stopped producing milk. For two months she was posted on Craigslist but barked at anyone who came to take her. When I showed up pregnant she laid at my feet. It was truly meant to be. We’ve been together for 10 years (she’s about 14) and she’s always next to me. She handles with just a few clicks and whistles, and is very tolerant,

Except for one thing—-she gets really mad if I sniff her 😅😂

Her coat is so fluffy and smells so good after her grooming. But if I take a sniff she snaps. She hates it!

I know the photos and backstory are unnecessary to the point, but totally necessary to our hearts because we all love dogs hahahaha.

So what do you think? Is it a dominance thing? Am I invading her space? Am I simply creeping her out? Does anyone else have this issue? Hilarious wrong answers welcome!