Would it work if any passive absorption was only enough to fuel her healing ability? The energy for that has to come from somewhere, and since she isn't aware of any abilities apart from her healing right now it would have to be a partially subconscious thing. It would only drain something like 5% from any attack, so the majority of the energy would still hurt her and get used up in the process if she doesn't see it coming and actively work to absorb it. In order to have any extra energy to work with, she does need to actively absorb it from her surroundings (attacks, sunlight, etc).

And if I understand the second part right, you're saying that she wouldn't be able to conduct absorbed energy through her body (damaging herself in the process due to the nature of her ability) then re-release it as the same form she received it in? Meaning that if she was struck by lightning, she wouldn't be able to channel it through herself and re-release it as electricity? If you're worried that it would simply be a rebounding of energy, it wouldn't. It would always have to go through her first, so if it was more energy than she is capable of conducting (ie, an attack above level 6), she'll end up either hospitalized or ashed.