I breed miniature smooth dachshunds and feel sure that your puppy is suffering from neglect caused by poor diet , if this is the cause it will take many months of good food to improve and may always have a strange gait, if she is a happy little girl I would give her time. In my last litter November last year my very small dachshunds bitch producted seven puppies and the second last puppy was born with her front legs across her chest and they have stayed that way. I have done many hours of physo on her and taken her to three vets for their opinion, one vet was an authopedic vet all were not confident she would do well. I refused to give up on her and she is now 4 months old, she does pit pat around but is having a lovely life, I really do not feel we have a right to snuff out a life if there is not a very good reason to do this.
Dachie