Just playing devils advocate here: Greenwald did previously state that he was going to send leaked information to his partner. So his partner isn't just his "loved one" in this. He would be one of the leakers.
One of the more hilarious examples: Miranda used to troll for blog posts that were critical of Greenwald and then argue with the bloggers, often posting the same comment (of fawning praise for Greenwald) to multiple blogs. When people realized the comments were coming from Greenwald's IP, it led to accusations of sock puppetry and lots of drama.
Point being, it's reasonable to expect that Miranda's involvement runs deeper than merely being in a relationship with Greenwald. Both past behavior and public comments suggest he might either be involved directly, or he's trying to appear to be involved. (There's a long history of activists inviting law enforcement responses; Rosa Parks didn't keep her seat just because she was tired.)
“When I was in Hong Kong, I spoke to my partner in Rio via Skype and told him I would send an electronic encrypted copy of the documents,” Greenwald said. “I did not end up doing it. Two days later his laptop was stolen from our house and nothing else was taken. Nothing like that has happened before. I am not saying it’s connected to this, but obviously the possibility exists.”
He said he didn't send it but implied he wanted to so it's very reasonable to suspect he did later at some point.
The data and the keys travelling together would be a pretty bad mistake, even knowing the keys would be a bad move.