Within Temptation is my top favorite female fronted band. I don't like the over-the-top opera vocals of bands like After Forever, Edenbridge, older Nightwish, older Sirenia, Epica, etc. I also do not like "beauty and the beast" style vocals where the awesome female vocals are slaughtered by the terrible animalistic growls (Battlelore is just one of several examples, although for some reason it doesn't bother me as much in Leaves' Eyes). Female fronted bands I like must follow the same rules as the male fronted ones: if their vocalist is not appealing to me, then they won't impress me much. It's just that simple.
Now, as far as female fronted bands that sound like Katatonia goes....I don't know any in particular. One thing that makes Katatonia such an extreme exception in this genre is that (at least currently) they do not use the male grunting/growling stuff. Until I discovered their nearly perfect blend of melodic vocals with darker music, I always had to rely on female fronted bands (or Tool) to fill my desire for heavier/darker rock music without the "harsh" vocals. Lacuna Coil used to be awesome in their HALFLIFE EP - COMALIES days.
LACUNA COIL:
Autumn, perhaps, is the closest to Katatonia that I can think of. They do have a darker, more subdued sound and the vocalist (like Jonas) doesn't have a wide range, but her voice works great with the music. Here are a few of my favorite songs which I could imagine Katatonia doing (some of their newer/lighter songs at least).:
AUTUMN:
Angtoria is another decent female fronted band with a more brooding sound.
ANGTORIA:
I also love tons of others like Lunatica, Brave, La-Ventura, Era For A Moment, Delain, Echoes Of Eternity, Delight, Evanescence, Lullacry, Fountain Of Tears, We Are The Fallen, The Birthday Massacre, etc. but none of those resemble Katatonia.
Jack