How would that work then?
When was the last time you checked the browser history on your computer for anything off? Or if you're someone who knows nothing of CLI/Power Shell etc etc, when was the last time you checked your command history? Do other people have physical access to your computer? Do you check it all the time? A lot of people don't even know all the browsers that might be installed on their machine (how many have Chrome, IE/Edge (perhaps both), Firefox and Comodo Dragon installed, yet only use one?)
Do you keep a close eye on all the software on your machine and make sure nothing else has been added that you've not noticed? Few people do that, even people who're somewhat IT/security knowledgeable - especially if they trust their housemates to not mess with their stuff or think they're secure enough that the housemates won't ever guess their password?
Is there someone out there using your name and address etc on a service you don't even know exists? Or perhaps using an old forgotten account that you set up a few years back for a single use? Most El Reg readers probably use fake details for those things, most other people probably don't.
It's likely she was using windows. How much of that is still exposed over the network in a way that makes remote access relatively trivial?
As to her creds on the C1 machines - maybe she has a locked desk drawer with a notebook that has her old details in it? The sort of desk drawer that is commonly very cheaply built, with a lock that keeps honest people from accidentally opening it and anyone else knows can be defeated with a plastic ruler/credit card or gentle tap in the right location?
I can't say she was framed by someone in her house or even someone else who knows her, but I can say that it reminds me of the scene in "Minority Report" where one of the cops talks of "an orgy of evidence", ie too much evidence pointing to the person.
Some criminals are just plain dumb, some make big mistakes on trusting their skill and home-grown encryption, but even taking this into account it raises a few red flags for me. (Of course, her defence will be quite telling - if they push for a 'framed' angle then it suggests it is possible, if they don't - it should be easy for a decent lawyer to introduce enough 'reasonable doubt' by saying a house-mate may've framed her).