When Remy had taken Edward from Tony's arms and let him go over to Pepper, she left the room because that was something she didn't want to watch, or hear or contemplate in any fashion. She went to go change her kid's diaper and try and distract herself from however it was that she was feeling.
Pepper hadn't really moved when Tony came over, not giving any indication that she knew he was there that was until he had spoken to her. After he was done, her eyes fluttered open for a moment and she looked up at him. She looked like she wanted to say something maybe, but her lips didn't really move. Then her eyes shut again and this time she didn't wake.
Her body went kind of limp, and her heart slowed all the way until it stopped. The tattoo continued to slide up her body, taking over every inch.