Depending on how strong of a reader she is...There is a really great series called the 39 Clues, very action-adventure oriented. (Brother and sister on a quest around the world...my DS has read a few of them.) But they are quite a bit harder than MTH or Junie B.
For not girly reading a touch easier...My Weird School(easiest) or My Weird School Daze (slightly harder)--set in a school, wacky teachers, etc. What about the Judy Moody books--or the ones about her little brother, Stink? Geronimo Stilton are fun/funny too--a little bit silly, and lots of pictures, it's about a mouse who is the editor of a newspaper and has all sorts of adventures.
Oh...thought of another series...If she likes history ( since a lot of the MTH books are based on historical events) , there is a series where every book starts with the words "You wouldn't want to..." and they cover topics ranging from ancient egypt, to america, and a lot of stuff in between. My DS's current favorites are YWWT Sail on the Titanic and YWWT be a Civil War Soldier. Lots of cartoony pictures, but good information in there too. I'd put the reading at a touch harder than MTH, but not much.
Fun topic, hope I gave you a few ideas. Happy Reading!