Thanks both of you!
I would personally stop doing this right away. It's a method that's unfortunately gained traction online, but can backfire badly with the wrong dog, creating an issue that never would have been there otherwise. A dog that trusts you not to randomly take things away for no reason after you've already given them to her is a dog that has no reason to ever become possessive. Taking away her food and giving it back to her, or messing about in the bowl (I don't know if you do that, but some people do) isn't necessarily showing her that it's okay and she needn't worry.
Good to know; I was told to do that by the breeder of my first puppy (Bernese Mountain dog, 20 years ago) and have been doing it with all my (3) pups. Never had an issue with possessive behaviours.
We are in puppy class - it was today, and actually we are skipping the last 3 classes and getting moved to intermediate dog training because she's too awesome. (#proudmom)
The trainer held her leash and distracted her while I was petting, playing, and giving treats to another puppy. Zola (my dog) was getting whiny and irritated, but then would quickly draw her attention back to the trainer as she was showing her toys and calling her name out. She ended up being pretty ok with it. When I got back to her she greeted me like she hadn't seen me in hours though. I just calmly took the leash back and told her she was a good girl, pet her once, and sat down at our spot. Zola lied next to me and waited for the next command. Other than that (when she has her human with her) she's awesome.
She suggested I go to the park with a friend and do the same thing a few times a week, so she gets used to me interacting with other dogs and realizes she can still have fun if that's happening, and see that I return intact every time, so there's no need to worry or fight off anyone. She also tested me with humans (hugged me and asked me to go hug a girl in our class) and Zola didn't even flinch. She'S like "oh yeah you do this all the time, all good".
Also my best friend is most likely getting a puppy in the next month so that might help ...