Reactive, Fearful, Separation Anxiety

Adopted a rescue pit mix a few days ago. I have been given a ton of handouts and resources about her, as she’s considered a shy dog and dog-intolerant. She seems constantly overwhelmed, to the point that she is over her threshold for commands while inside or outside. High value treat training is not an option, she is uninterested in any food while outside or scared inside.

I have read a lot of posts on here, as well as the FAQs on reactivity and separation anxiety, and even the first steps don’t work for her, as we can’t figure out what positive reinforcement looks like. She’s dog intolerant, so no group training or socialization classes for her either.

She is sweet only toward me. Fearful around the rest of my family. I know about the rule of three, but this is a nightmare and i’m worried she’ll never warm up by 3 weeks. She was not flagged for leash reactivity, barrier reactivity, or separation anxiety in the shelter. This seems like a total behavior meltdown in her new environment. We are trying to establish her routine, but she won’t even settle down to sleep unless i’m in the room with her. I’m at my wits end, and it’s only been a few days. Please help me, i’m seriously so lost. The sudden onset of all of these unknown behavior issues is really really becoming hard to overlook or manage.