still looking for an answer to this
There is ordering the case notes from the TRV application. Ideally you'll get a more detailed explanation why she was rejected, but there's also a change you'll get vague and generic reasons, depending on the officer's mood.
https://atip-aiprp.apps.gc.ca/atip/welcome.do
It'll take $5 and 30 days (and her signed consent form), and then you can decide what course to take, if you should reapply or not.
Sorry to have to say this, but many cases like your girlfriend's are rejected. It's not impossible to get approval, but chances are very, very slim.