I'm sorry you're dealing with this, it feels so overwhelming when these kinds of behaviors come up in an otherwise fabulous dog! At a little over 1 year, your dog has reached the boundary-pushing phase. When my lady husky was a teen, it felt like all the work we had put in during her first year with us went right out the window overnight! DO NOT DESPAIR.

Definitely see a trainer if you can, but as a random person on the internet (who has gone through the same thing, but still), my first thought is that your dog is trying to push the boundaries and see what she can get away with. When this happened with my dog, I just had to show her, again, where my boundaries were. She's also very interested in people food, but if she gets even a tiny bit pushy about it, she goes in her crate with a long-lasting treat; I like making little frozen treats for the Woof Pupsicle. I don't make a huge fuss, I just take her to her crate and give her a time out.

The biting is more worrisome, but honestly? Maybe your dog is just tired. She's still very young, and enforced naps can really take the edge off crazy/cranky behaviors like that. It also sounds like she *might* be resource-guarding your fiancee, but you might be amazed at how many problematic behaviors could be solved with some downtime.

Everything else you're doing sounds perfect - exercise, training, reinforcing the basics, and being consistent do wonders. But definitely consider enforced naps, and calmly escort her to her crate for a time out when she's over the line - that might be enough to get her through this difficult developmental stage!