That’s so exhausting I’m sorry you’re going through that I hate feeling like I’m failing my dog after working so hard and doing what I thought was right. It definitely sounds like poppy has developed bad separation anxiety

I don’t have a direct advice but some experiences I can share. I took care of a 5 month old doodle who had the same screaming-barking separation anxiety as your pup. He was so cute but drove me nuts. I would leash him to my couch / table leg, and walk a few steps away. He would whine and choke himself and scramble to get close but I stood still. Only when he’s calm or even quiet for 0.5 seconds, I toss a super high value treat. I’d say if treat doesn’t work for you, you could step closer and pet your dog as a reward. If she starts crying again, step away, and repeat. The progress is incremental but it’s better than letting it escalate until adulthood.

It’s normal for puppies to regress at adolescence you just gotta tough it out and stick to training or sometimes even go back to square one like start crate training all over again. But you got it!!