but seriously one i watched when i was younger was monster rancher, was awesome and had its dark bits but all in all really good.
Also another called Shizo, both are really good and are for younger viewers =]
Also what you have to tell her is that japanese and american shows are very different, if she's used to american shows it'll be hard for her to make the switch as japan do very good bad guys whilst america always have theyre bleeding cheesey parts.
Detective Conan seems like a childish anime, but from what I've read, people think it's scary.. o.o
Sailor Moon? Lucky Star? Shugo Chara? Ouran High School Host Club? Lilpri? Not Elfen Lied. Might be too scary.. xd
It really all depends on your definition of childish. If you mean you want an anime for a young child then something like K-On or Nichijou would be better for them. However if it's something more slice-of-life and just outright funny, Gintama or Sket Dance is the way to go.