This is a very common issue after a dog has been attacked by other dogs. A muzzle will prevent her from actually biting another dog, but it won't change the feelings she's having about them. She's afraid, which is why she's behaving this way. She needs to know you will keep other dogs away from her, so she can relax. A muzzle is fine to prevent an accidental bite, but it's only part of the solution.
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