I blooming love cats, but can understand how frustrating this must feel.
As others have said, 10 weeks was a long time to be away from home. Although it seems that she wasn’t quite so bad there, so I agree with others that have said maybe she needs a more contained area for a short while. Am guessing that’s not easy with two teens in the house, but have you got a room that could be her space?
I see you’ve installed a bigger dat flap. Does she go out much? Does she seem to prefer being out or in? Have you noticed whether other cars visit your garden? This can really stress them out. Maybe some privacy film on lower parts of windows if she prefers being indoors.
If she prefers outside, do you have a shed or something that could be converted so that she has access to somewhere warm and set up for her needs?
I’d definitely discuss anxiety medication with your vet.
Have a look for a Jackson Galaxy videos, am pretty sure there are a couple of episodes dealing with this sort of behaviour.
I am not sure if sending her to any rescue would be the best thing for her. Whichever rescue, it will be more time cooped up, then adjusting (or not) to a new home - and any new owner may not try everything that you have. Equally, I don’t like suggesting PTS, as I feel that when we take on a pet, we take it on for life.
Just throwing out random thoughts here!