They seem a bit more stubborn now, but plot resetting DOES work. It actually works better, because villagers won't mow down QR codes...unless there's no possible spot for them to plot.
Just keep at it. She will eventually move to a new spot.
If you want to possibly make it easier, do it this way:
Change your 3DS clock (not the game clock) back to yesterday, or whatever day you asked Molly to move in
Go around and start slapping down QR codes
Any spaces you would like to see her plot into, leave a 3 x 3 area open. Technically it's 3 x 4 for their door, but others have said that that doesn't matter for their plot.
Save, set your system clock back to today and continue plot resetting.
^^ This actually works, I tried it yesterday with Deirdre because I missed a spot, I got advised to TT using the 3DS clock and place patterns down and TT back to the day she moves in and it worked, she was no longer favourtising the front of my house. Good luck c: