Nah, I've played Jo as Bobby's stepdaughter before, so that's perfectly fine with me. It'd probably be easiest if Ellen were dead too, just for simplicity's sake. I'm also cool with Jo (or let's go with Sarah?) hanging with him more lately, and yeah, she could have definitely shot him down. Probably with something like 'once burned, twice shy' kinda deal.
I'm excited!
Also, I was figuring (since deceased chars come in from just before their deaths) of her being in the hospital as the victim of a wild dog attack when I first start her out, just so you know ahead of time?