I'd say it'd be something more along the lines of sending out a spell that uses an equal amount of mana to nullify the incoming spell, cause something that sends the spell back to the sender would just create a ping pong match. So she either has the choice of completely nullifying one spell, or using one of her offensive spells to intercept and attempt to destroy the other spell.
Try not to think of it as MMO levels, but that sounds like a fairly interesting idea. So she can use all of her spells and use any amount of mana on them, and in exchange can bring out different effects from said spells? I'd say that she shouldn't be able to break rib cages that easily though. Perhaps, ICly, (with training and such) she can perform delayed spells, where she basically casts the spell beforehand, and saves up the effect for the future?
Try not to think of it as MMO levels, but that sounds like a fairly interesting idea. So she can use all of her spells and use any amount of mana on them, and in exchange can bring out different effects from said spells? I'd say that she shouldn't be able to break rib cages that easily though. Perhaps, ICly, (with training and such) she can perform delayed spells, where she basically casts the spell beforehand, and saves up the effect for the future?