First of all, don't panic. It is OK! It isn't whether they are positive or negative per se, it is whether they have an "incompatibility" with their OWN positive/negative other blood reading. Anyway, no one can "make" you take your baby back to the hospital! She is YOUR baby, YOU make the decisions. Our first and our fourth babies had this issue, and yes, they were a tiny bit jaundiced, but not so much as to NEED the lights (like when they risk being brain damaged because of off-the-chart numbers, and some moms here can tell you what those numbers are, I've forgotten.) Ask that the medical personnel tell you her numbers and also ask what the danger cut-off is. Ask for the absolute, undiluted, unexaggerated truth about this, because you are more likely to get the truth this way.
Does she have jaundice symptoms? Yes, there is asymtomatic jaundice but this is pretty rare. If her skin or the whites or her eyes are yellow at all, just start nursing furiously, and be sure to strip her down naked except for a diaper, and sit in the sun with her three or four times a day for 15-30 minutes each time. Not in the hottest, sunburn time of day, but just enough so that some sun exposure will help get her body to process that bilirubin. Heck, nurse furiously anyway, it will only do her good. Certainly it will keep jaundice at bay, unless she has a serious case of it (unlikely.)
The bili-lights are rather controversial. Be sure to get lots of input from moms on this list. With our baby born in October, she was fairly jaundiced at birth, but I refused the lights and nursed like a fury, and sat in the sun with her by my hospital window every time there was sun. It worked like a charm. If her numbers had gone way up, to the danger point, yes I would have done the lights. I'm not going to let their health be in danger. But it certainly was nowhere near that point, and my hunch tells me that your baby isn't either. So many docs are scaremongers. UGH.