Jo, you haven't had her that long, have you? Remember that dogs, no matter the age, have an adjustment period when their entire existence is changed. And, you now have to teach her how you expect her to behave. BTW, I have never been successful in teaching my dogs how I expect them to behave, but I hear that is what you're supposed to do, LOL! Seriously, though... she may still be adjusting, she may be afraid, she may have had issues from her earlier life. I trust you and she will find the right balance.
Brenda