She doesn't wake up, just feels a body pressed against her and instinctively nestles into it, throwing an arm over him. She hasn't shared a bed with anyone since Tom - probably subconsciously thinks he is Tom, even if he's too skinny and tall. Though it hasn't been as long for her as it has for him, Martha likes physical contact, and she's felt a bit starved for it lately.

This probably explains how her head ends up pillowed on his chest and both an arm and a leg are slung over him a few hours later. She'll probably be incredibly embarrassed when she wakes up, but right now, she's blissfully comfortable after a rough few days of trying and mostly failing to sleep.