@jamiem Hey - I wanted to reply a few days ago but I also wanted to read through advice in this thread in case I gave you anything that had already been covered, and I don't think this has directly yet so I wanted to point it out.
Firstly, make sure to give yourself time as well away from the dog and looking after yourself. It's true that they pick up on our emotions, things like frustration (even if it's not AT the dog but at the situation). Give the dog something to keep them busy in their crate and look after yourself.
Secondly, you said she's a year old. I know she's big and strong, but she is still mentally just a puppy and the world is still new to her! This is a great opportunity for you both to bond, once you've looked after your own needs! A lot of what you're saying could be youth and inexperience vs a traumatic experience (not discounting that it is scary when she reacts, of course!)
I have a largeish dog who we have been working with since we adopted him a year ago. He is reactive only on leash and we've isolated it to primarily dogs, though he has also mistaken prams/strollers, carts, scooters and people for his triggers
The things you're saying about how your girl is unpredictably reactive? Totally relate. Super happy in one situation with the neighbour's dog and then frenzied creature from hell in what seemed like the exact same situation another day.
The things we've worked on that are working for us - and I know this isn't going to apply to everyone, nor am I a trainer, so just think of this as possible other ideas:
- Impulse control. From day 1 I worked on waiting before dinner, doing the 'its yer choice' game, a trick (eg sit) before kicking his ball/playing any games. Helping him understand that he can think before doing.
- Engage/Disengage. This sounds like what you were doing by just existing with her, but in a structured way and building up over time. For me this was standing 100ft away from a dog park and rewarding every time he looked over at the dogs, then moving closer by 5ft, repeating a few times, then going home. Then the next day we'd start at say, 90ft and work closer. I think about it like 'building up his resilience to weird things happening', really slowly. The goal is to NOT react - so if he gets too amped, we take a step back. Oh and for this I had to use GOOD treats, not just kibble. (Think hotdogs, chicken, steak etc)
- 'Let's go!' (changing direction when on leash unexpectedly, saying the cue, and working up til he just responds without pressure on the leash). Basically this is my 'get out of dodge' technique if I need to change direction to get away from a trigger. You mentioned her reactivity to dog shaped objects - this skill helps you both avoid those entirely if you can vs her staring at them.
- Lots of 'chill out' games: scatter feeding at home in grass or in a toybox, snuffle mats, frozen kongs, lick mats, mat games, etc. Helping him regulate his own emotions.
The biggest 'aha' moment for me was realising he's unpredictable and reactive because he's anxious and he has no good alternative behaviour than freaking out on leash, so my focus has been building up his confidence and also in turning to me rather than lashing out at the 'thing'. I also get really embarrassed trying to get past people with a crazy dog on a rope so I have been working on how I react/respond in those situations too. And I don't use aversive tools because I think they're counterproductive to building confidence the way I want to.
Some dogs are reactive for other reasons, so the other advice about talking to your vet, seeing a trainer or behaviourist etc are good!
I had to go find the pic of your pup..she's beautiful