You can tell your girlfriend that an x-ray is usually not that useful for minorly broken ribs cos what the fuck can the doctor do, they can't splint a rib. The real danger here is a chest infection; it's one of those things where broken ribs are usually minor and a chest infection is usually minor but if you get them together then OH NO. If she feels the need to worry about something then she should worry about that.
She can also take you for long walks during which you do lots of deep slow breathing. Possibly while holding hands. That's something girlfriends are often very good at helping with.
On the note of chest infections, try not to get covid. Like, this is general good advice, but especially now.
I am not a doctor or a surgeon or anything, just an antifascist medic, so if a real doctor contradicts me then go with their advice.