DIFFERENCES BETWEEN A WITCH AND A FAIRY GODMOTHER

1. A witch will not hesitate to blast someone away if they are getting in her way.  A fairy godmother will prefer to turn said pest into another species - usually a frog or other amphibian.
2. A witch is quite happy to have a house made out of sweet stuff with the idea it will entice kids so she can cook them.  A fairy godmother will warn of the dangers of the sweet stuff on teeth and point out she is on good terms with the Tooth Fairy, who isn't always as gentle as she could be.  (If that last bit doesn't put people going after a sweet house, nothing will).
3. A witch will turn up and spoil a royal christening.  A fairy godmother will appear after that and undo or limit the damage.
4. A witch will think twice about challenging a fairy godmother as she knows the latter can defeat her magically if pushed.  A fairy godmother will not  think twice about taking on a witch if she feels the latter's behaviour merits that.
5. A witch will go into alliance with a wizard if she feels she can gain from it.  A fairy godmother never would do so as she knows the majority of wizards are treacherous so-and-sos.