Sitter for unsure, anxious dog

I’m looking for some advice because I’m navigating a new situation with my dog and want to set her up for success. My dog is a small Cavalier (3) who is generally very sweet, smart, food-motivated, and does great at the groomer and her regular vet.

Last year she had to go to the ER vet that seems to have made her more unsure when someone enters our house, especially when I’m home. She barks at first and needs a few minutes to feel safe, but she does eventually warm up once things are calm and I’m not in the mix. Or if I keep her on her place, she’ll bark a few times and wag her tail SUPER excited for me to let her off (not an anxious wag, an excited wag) I’m learning as long as no one reaches towards her to pet and respect her safe, she is able to stop barking and learning that she can simply walk away.

Here’s the situation: I have an event coming up and none of my usual sitters are available. I’ve never used a brand-new sitter since her ER incident, so I honestly don’t know exactly how she’ll respond. She will need someone to come to the house, let her out of her crate once, clip her leash to her collar (she’s an escape artist, so I’m avoiding a step-in harness), take her out for a quick potty break, and then put her back in her crate with a treat. No petting or handling is needed beyond clipping a leash.

My concerns are that she’s wary of hands reaching toward her if she’s overwhelmed (she has air-nipped before) and I want to make this as stress-free and safe as possible for both her and the sitter. Before this she has had a handful of random people watch her and she’s been excellent.

What’s the best way to introduce her to a new sitter so the sitter feels confident and she feels safe? Does a short paid “test run” or meet-and-greet usually help in these situations? Again – she is excellent at groomers, vet, etc. Anywhere where I am not.

Any advice from trainers or people with anxious/shy dogs would be so appreciated. I just want to do this right and keep things low-stress and safe for everyone. Have worked with many different trainers to find what works for us and although I feel confident handling her, I am unsure of how she’ll be alone (with my moms dog who could care less) with a new sitter. I’m thinking a few stop by, give her treats, repeat kinda moment. This really stresses me out so please nothing unkind. 🥲 Thanks so much!