Nebula glared at Quill's assessment of her looks, Gamora was right they should just kill them all, Quill included. But that was likely the aches talking and not the part of her that did actually have some measure of affection for Quill and some of the other Terrans.
She looked around them when he told her the fresh air was anywhere outside and breathed in deeply, "No - this air is not fresh." She insisted, "It smells no different than the air inside our home." And if it truly were fresh she had no doubt it would smell better, different in some way to what they were breathing in regularly. And if this was fresh air she would feel better now as well.
"You don't look like shit," She said after a moment of internal debate about the quality and healing properties of the air around them. "What have you done?" She asked eyes narrowed as she looked at him with some measure of suspicion.