As A Leo who knows a bit about the sign I do think it would have been a little bit more traditional to go with fire for the element choice, yet the story is a good one, and I do think war like lions with fire powers (rest of her tribe) does sound like a good concept.
Little nitpicking: I don't know what have you exactly thought with "incorporate an element", but traditionally leo's element is fire and not the earth (which the flowers would indicate). So I'd be interested to hear if you have some story or anything to clear your choce here.
As for art itself, I like your lineart quite much, and you have done good job with playfullness of cats here.
when i created Zodiac Leo, i didn't know that the zodiacs had correlating elements. i did flesh out her story a bit on my newgrounds submission's discription:
"unlike other lions from her tribe, leo does not enjoy the thrills of combat and prefers to find solace in the forests. She learns that she has a hidden power to communicate and control plant life itself."
perhaps the other lions in her tribe can harness the power of fire? It would make a very intresting story concept.
It's lovely - the colors are great! In terms of critique, the only thing I can really think of here is that her upper chest seems to be tweaked a little bit? Her hips point off to her right and her shoulders point off to her right, but her chest is basically straight ahead. Also, her right arm is noticeably smaller than the other. These are things you might be able to tweak a bit digitally, not huge problems. It is very nice!