If it was me I would get 5 accounts for myself and one for her. As it sounds like you know already it is pretty good to have someone else heal while you dps in pvp (4 + 1). The 5th account for yourself would allow you to 5 box when you want and also allow you to have more possibilities to substitute into your team. This is very beneficial if you start to do mixed teams where you might not have all of the different toons you want on every account (some people level a few groups of 5 of all the same type and then get tired of it so start to mix it up so they may not have all of the different character types on every account).