Need some help!

I currently have a six week old chick in the house with me right now (momma abandoned the nest to be with the other chicks while she was still pipped). So, i brought her inside and helped her hatch out, and by the time she was strong enough to be with the other chicks, momma wanted nothing to do with her. She now spends a few hours a day outside with all my other hens and they all get along, but i bring her back inside for the night because I fear its too cold for her to keep herself warm all on her own. Its been getting down to the 30's at night. Will she be fine out there on her own? Does she maybe need a heat lamp? Any advice would be appreciated!!