The concept that she's a barbarian and will miss sessions reminds me of the Gamers. Have you seen that move?
Having a not 100% attendance person is the pits if the way you handle it is that their character just isn't there when the player isn't there. I've been in games where an absent player has someone else run their character so the character isn't absent. It's not a perfect solution (nothing would be), but we found it preferable to weird story excuses for a character's sudden disappearance.