Mia is a 4 year old lab cross (lab x pointer, we think), who we got from the Dogs' Trust in Glasgow about 6 months ago. She hadn't been with her previous owner for long, and before that, had had a couple of litters of puppies. When we got her, we were warned that she was insecure - she'd become very over-attached to her previous owner - and we were aware that there might be problems.
In general she has settled in pretty well, but there are a few things that still worry us, and we'd like to sort out for her - I suspect they might be down to insecurity, but we are not sure how best to help her.
She is a very barky dog - whenever someone comes to the door, or walks past the end of the drive, or, in the case of our neighbours, has the unutterable cheek to walk or drive up their own drives, and she barks and goes nuts when we get home from anywhere, especially when dh gets home - she is most attached to him, and can be a bit jealous when he gives attention to other dogs, including ours. She isn't aggressive with it, but glares, or barks, or tries to push her way in, so she's getting the attention.
Today dh tried to take her on the ferry to Cumbrae (something he has done with ddog 1 before, but not with Mia), and when the point came to walk onto the ferry, she literally shat herself - with fear, dh thinks. He cleared up, and waited until everyone else was on board, and tried again, and she had another bout of diarrhoea, so he abandoned the ferry, and took them on the train along the coast, so they could play on the beach, and swim - and she was absolutely fine - no more digestive upsets at all, which does reinforce that it was a fear reaction.
We don't let her get away with jealous behaviour - we reassure her, but other dogs, especially our other dog, get plenty of attention, and she does have to wait her turn.
I've tried using gravy bones, and the command 'quiet' to get her not to bark or to stop barking when people come to the house or walk past, but although she is a very bright dog in other areas, this lesson doesn't seem to be sinking in. The barking seems to be excitement, and if she gets to the person, she doesn't jump up or act aggressively, and will stop barking and be her friendly self when she has greeted them. She only jumps up to dh or me, for a cuddle, and will get down when asked.
She does occasionally do a sort of grumbling growl, if she doesn't like something that his happening - eg ds1 trying to put her lead on and take her off the couch for a walk (she wanted to stay with me because I had a fish finger sandwich and to a lab cross, that was more immediately appealing than a walk) - but we did enforce the behaviour we wanted, and she stopped growling and went for a perfectly happy and well behaved walk with ds1.
So, dear doghouse experts, does this sound like insecurity, or is it something else? And what can we do to help her settle down and become a happy, secure member of the family - we love her very much, and it worries us that she may not be as happy as she should be.
Could she still be worrying that she will get taken back to the shelter, as her previous home only lasted 4 months or so?
Any help or advice would be gratefully received - we have considered consulting a local dog trainer/behavioural expert.
Apologies for the essay, and congratulations if you have read this far! 
