@P**
, (I took your advice and deleted most of your comments due to relevance)
Just so we're clear medical extensions of stays go thru the immigration staff doctor who reviews the treating physician's recommendations that a person not be allowed to travel or that a person be allowed to get an extension based on being the care giver of the sick person. They are the person who ultimately decides IF an extension due to medical reasons can be issued.
Personally, I've only seen those "care giver" medical extensions be issued for immediate family not in the instance of a girlfriend.
If I was a betting man I would bet they would be denied an extension because they are certainly able to travel and a border bounce (no matter where you are in thailand) doesn't take more than a day.
Still it will be interesting to see what transpires IF they do apply