new puppy

I just adopted a puppy from a shelter to help me deal with my grief. she is a german shepherd mix, 4 months old. I gave her a chicken flavored edible chew bone and it got stuck under the gate. she was trying to get it out and I went to help her and she growled at me. I was so surprised I didn't know what to do. I said "hey" or some other inane thing and when she wasn't looking took it away. I can stick my hand in her food bowl no problem and take toys out of her mouth but she turned into Cujo with that chew bone. how do I correct that? we're starting puppy training next week so that will help but what do I do in the meantime? also my cats hate her and are having a really hard time. I feel terrible for them but I want this to work out.  I have only owned 3 dogs in my life and I raised and trained them myself. I've never had this problem before. except for that one incident she is as sweet as can be. she's very affectionate and rolls over on her back for belly rubs and she's very smart too. there's also a problem with submissive urination when children come up to her.  only with children though. I wonder if she had a problem with kids in the past. she was found on the streets and then she was in the shelter for a while.