None of my nine wear a collar. They compare it to some horrid type of torture! They can twist their bodies in ways that are unbelievable in an attempt to remove it!! Mine were all ferals too but older than your little baby. I would put one on as soon as possible so she could start getting used to it. I don't think you will have a problem if you start soon. Collars are definately a very good idea.

Good luck with your new baby