@Notaurewhattodo
I just don’t know what to do for the best. I could persevere for a month or two and see if she settles but it would be kinder for her to be rehomed young
Honestly, you haven't broken her or done anything horrendous. You've just taken advice from a breeder that didn't allow for a more nervous dog.
Really ALL you need to do is take a step back. Keep her in your house and garden, play with her in short spurts, let her sleep on you, get used to you. Walk through the house calling her name, so she gets used to following you. You could even start to train sit, down, paw, her, wait etc, find out what treats she really likes, play with her.
Do all of that inside, then in a different room, then with someone else calling her back and forth. Repeat in the garden, alone and then with someone else as a distraction.
And keep her very short wee walks to quiet times, from your door and back again. 5 minutes is enough, remember her paws have to get used to pavements! Repeat all those commands whilst walking, say at a kerb, anywhere you want to have her attention.
Build that up.
Other play would be chewing and leaving a favoured toy, swapping it for a treat - but that's quite a feat at her age (or even 2 1/2 like our Toad). But learning to chew things she is given rather than you or the furniture. Get a few dofferent textures for her to chew.
In a week you'll feel very different, so will she!
And yes to a crate. Some don't like them but a nervous dog may well get a lot out of having a safe space, one that no human ever reaches into! Ours only sleeps in his, but seems to like the safety, the dark (drape a blanket over it) and sleeps almost as soon as he goes in.
Take a deep breath and just start again, slowly. You'll feel far less anxious and so will she!