I can see Gisela driving around on a moped and being part of some sort of gang. Perhaps having once been a great cyclist or motorcyclist before some kind of big injury which lead to a life of crime.
About Gertrud as a Puella Magi: She had bad self es-teem because of bullying but a love for flowers (roses being her favorite) so met kyubey while crying in a rose garden (because she ran away from the bullies) and wished to be beautiful like a rose, maybe she becomes a witch when she finds out witches are puella magi and then she hates her self even though she was beautiful on the outside so she became a witch because she couldn't take being herself anymore.