IIRC - and my memory is certainly not perfect - Ballard's situation isn't quite comparable to Tuvix, nor is Quinn's although they all do share some common factors and difficult choices. Ballard was KIA on a mission and was later restored to life by an alien race who resurrect dead aliens as one means of propagating their species, and who gave her body altered DNA and memories. It's made clear in the episode that a lot of Lyndsay's original personality remained intact and that she felt she still belonged with Voyager, but she also had trouble remembering aspects of her human life and doing activities like eating Earth food, because her body reacted differently to it. And when her "adopted" family came looking for her and were perfectly willing to fight Voyager in an attempt to "rescue" Ballard, she finally elected to return with them on account of her partially confused memories and a desire to protect her former crewmates, even if she didn't like the idea. But it wasn't a matter of Janeway arbitrarily ruling against the possibility of her being welcomed back, or anyone else in the crew. Quite the opposite. Part of Ballard also felt at home with the Kobali and her "other" family. To be fair, in terms of writing, there are a number of issues with "Ashes to Ashes" (which was a later ep, S6). The quandary facing Ballard is rather interesting IMO, but some elements of the story seem a bit too rushed in execution to work as well as they could.