2nd spell: Just wait for the fiery master spark to pass you, and then graze on the opposite direction it's going to. Alternatively, just try standing behind her.
3rd spell: This one is a bit tricky, the attack itself is unblockable and ungrazable, so you have to dodge it the old fashioned way, moving left and right throughout the screen until she lands. Punish her with one or two combos, rinse and repeat. You need, above all, patience to get this spellcard without dying or "bombing".
On a sidenote, I'm surprised. I played some netplay earlier today and goodness, Koishi is actually good/fun to play as! I'm surprised since I expected her to be an awful character after playing one or two matches with her yesterday.