She's good in a fight and she's a good archer.
But i'm thinking of having J'zargo join me, he uses bad ass dual destructive spells, and he can use Heavy Armor but I think i'll use Light armor.
I'm thinking enchanted Dragonscale armor with Fortify Magicka and Regenerate Magicka, plus a ring and amulet.
That could be bad ass

Btw, her's a Companions Ranking: http://www.ugo.com/games/skyrims-best-companions?page=3