Rottweiler chewing/sucking on bedding

Question
Hi have got a 4 year old Rottweiler bitch. Very docile in temperment but she
does get aggressive and growl or bark when other dogs are near when she is
on the leash. Though she won't act the same when off the leash and around
other dogs. She'll happily play with them. Why does she get aggressive on
the leash but not off it?

Also she will also quietly suck/ chew on clothes or bedding sometimes. Why
is this?

Thanks jamie

Answer
It is often that the dog feels defensive on leash,a good way to fix this would be to use a muzzle,and let other dogs snif her,as she can see they aren't going to hurt her,while she can't hurt them-so do this for a few weeks

Now,as for her sucking,it is a common things dogs do and no one knows why-but if it bothers you,there's a product called bitter apple you can buy at any petstore and it tastes bad so the dog will spit it out