I've adopted a 2yr old whippet/stafford cross and i'm not terribly sure she's been socialised all that much with other dogs, or maybe she's a big bully, i'll explain.

If she spots another dog, no matter how far away they may be, her tail curls over, she gets a very obvious ridge of raised hair, her ears perk and she'll start snarling and barking. This has happened at training and we've been told to take her out until she's better behaved as she was upsetting the other owners/dogs. However if the dog starts barking at her first she usually doesn't make any attempt to growl or snarl, though it doesn't always work out like that.

With people she'll start growling if they approach her or attempt to stroke her, or me, she gets very worked up if they enter the house. I'm not sure this is so much her being under socialised or perhaps her believing she has to protect the house because the humans are obviously hopeless at it, or something along those lines. Once she knows the person (several weeks/months along the line), and they haven't made attempts to touch her or others in the house, she tends to calm down around them, but if they speak to her or attempt to scold her for doing something (which a few relatives do attempt to do) it sets her back.

I'm really not sure how to go about working on this, unfortunately all the dogs we've owned before have been fairly happy-go-lucky JRTs. She is fairly OK with us, I know she wont bite or lash out at me, but she has been known to do so with other members of the family. I'm assuming this would be more to do with dominance than anything else? I can pretty much do anything with her and she is quite obedient, even off leash which is something the others weren't so great at, but the way she acts with other dogs/people worries me.

She is quite possessive, whilst she is great with cats if one of them jumps up onto me she'll start barking and snapping at him. She is a lovely dog but as i've never come across this before with any of the others, i'm used to normal scraps between dogs but she doesn't seem to understand when the other dog has submitted.

Her behaviour does worry me as the moment they see her or hear she's part whippet they can't believe she reacts the way she does. I was considering looking up a behaviourist but the OH has put his foot down about it, he doesn't view her behaviour as a problem but more of an entertainment, which to be frank is annoying me as i'm sure if she were a great hulking thing he wouldn't find it so amusing.

Sorry about the rambling, I wasn't sure what to put.

From what you say about her stance and raising her hackles, I'd say she does show all the signs of having been undersocialised :(

Socialising even a pup needs careful management, but with an older dog you really need to be careful to prevent the dog being asked to face something it's not ready for, and then having to deal with the potentially dangerous results :(  If you can persaude hubby to consider a behaviourist (preferably one recommended or by your vet, or even better - get a referal from your vet, your dogs health insurance may cover this) as they can observe the dog and help to guide you towards helping her realise the world isn't such a scarey place, but you do have a long haul infront of you.  If you got her from a rescue, they may be able to put you in contact with somebody who can help.