I would pick something that complements her abilities or lack of abilities. The toon would need to provide holds/immobilizes to keep baddies in her sweet freezing rain and whirlpool. Your AoE immobilize will help with all of your daughters kb. Earth, Plant, Ice (to fit thematically while duoing with storm) and Fire troller would all fit the bill. Earth best controls around. All I need to say about Plant is seeds of confusion. Fire provides more dmg along with good controls to go along with all of your daughters damage.
As for secondary, you can't go wrong with /Time, /Nature, /Dark, /Rad, /Elec. Aff. (depending on primary elec can be busy...too busy) ,/Kin (but remember she'll probably be at range missing the taoe buffs), /Storm (more dmg but neither of you will have endurance).
Hope this helps you decide if picking a controller.