Well, what I generally do with her is this:

[list]
 [*]Have Meltdown in her command list. Go far, but not too much, and charge to the max,[/*]
 [*]When you use Fire on the ground, you can combo with Firaga instead of chasing the CPU.[/*]
 [*]On air, I have the Holy Combo. Use it, continue attacking with Flare (X) and then at th 3rd or last Flare, press Square and you'll combo with Ultima.[/*]
 [/list]