It's not cheating, it's just using her resources in full. She'd feel stranger about the influence but they've been linked together to some extent nearly all day; synchrony is easy between them but it's not inevitable, it's always an offer and acceptance. She doesn't have room to doubt that he doesn't want the help.

As he settles against her she's halfway asleep already, only reacting with a little puff of breath, satisfied to have him so close. There are lines they haven't crossed, boundaries she isn't sure they should threaten, but the truth is their relationship is intimate in a whole other way. Here, where that closeness offers so many advantages, she just can't bring herself not to leverage it.

She sleeps easily, though she won't be able to guess whether unconscious synchrony is a thing; it could just be the reassurance of having a trustworthy body at her back.

But eventually she wakes. Not scandalized, but a little bemused, trying to inch her way out from under his arm without waking him and calling attention to it.

Ok, in the light of day, maybe it's a little inappropriate.