Maybe "Sticking Together or Elements Unite" or somethin

Great story idea. It sounds cute, I would read it. For the title maybe:
Worlds Collide
Four Life
The Element Chronicles
That's really all I have for titles, it probably doesn't help, but I tried.
For the girl's name maybe:
Brooke
Marina
Whitney
Willow
Winifred
Wren
Wilma
Wanda

That is a nice story if u decide to write it send me a copy id love to read it and id probably name it The elemental sisters or elemental hearts. or somthing soft sounding and loving! but yes i would love to read a book like that maybe u could name the water controlleraquamarine or Lily or something that sounds watery or water related. as for the dark one i suggest looking up words in another language that mean dark, evil, death, things like that and find one that sounds like a name and use it it will add ALOT of depth to the name and give it a chill factor.

call it like.... ummm "Elements" just like straight to the point

great story idea!!!

Secrets of the Elements.
:S
or The Burden of the Elements.
or if yu want it too be snappy,
Elements Unite. :S idk lol
took me ages to find out the name of myy book.
btw that is an AMAZING idea!