I was just going to start with closing one or two but I could try that tonight instead... There is a crap ton of pressure though since all of the hvac stuff we put in is about 2/3x bigger than reccommended, so your way is probably better...kiba, I wouldn't shut those vents all the way, may end up with too much heat in the bedroom. My daughter has central air with vents in the ceiling, the bedroom didn't get enough cold air and she shut the living room vents off, she froze in the bedroom that night.... I told her to try just shutting the living room a little at a time and see how it goes, it took a few days of trial and error until they got a good balance but now it's even through out the house.
You could have your girlfriend slowly close the living room vents while the furnace is running and with you feeling the air flow off the vent in the bedroom, might help shorten the trial and error process.
At least until the new temp sensors arrive anyway. Supposedly that will completely fix my problem according to reddit. I pre-ordered 3, so I guess I'll put one in the dining room, one in office & one on the far wall in bedroom... Part of the problem I think is the new mattress, it's one of those new purple hybrid ones which is extremely comfortable but literally retains no heat. Probably will be nice in the summer but for me, ever since I was a kid, I feel like I lose half my body temp when I sleep. idk why.

I do like the idea of being able to control the heat from the bed, that is nice.