This reminds me of my beloved Pip, we got her November 2010, we started lambing December and if you recall, 2010 was the next really cold winter we had after the previous year. Mum was also more mobile, 7wk old pup, put out front door, told, "wee wee & a poo", she'd shoot to the little area that was hers, then run around to back of house to come in through a different door. When the cold weather came, we tried to get her to go out the back (enclosed area) where the old dog went, refused! When that dog died the following March, Pip went out the back, no problem. Then, a couple of months later, we decided to get another pup, (Flo), mum said she could go out the back with Pip, HA! Pip was like me, likes her privacy! REFUSED to go out the back for years, insisted instead of going out the front again (we even had a light put up for her!) She started going out the back again last year, we think for "safety" if that makes sense as a few days later we found out that she was blind due to SARDS. ( She coped better than us.) She died suddenly in April this year and I still can't get over it, she was my best friend.
Anyhow, we got another pup in to keep the other company and the lady who we bought her off hinted she was housetrained! Wee & Poo in the house several times a day for weeks! When we asked the seller, "oh it doesn't matter!" She said. Bloody does ! Dog is NOW housetrained, no pads, pushed through flap to the area that was done 20 + years ago for dogs doodoo! Cleaned every time mutts go! But this pup still has accidents, but no longer does it out of spite (out, I would tell her, she'd squat in defiance! Been 12 + years since I've had pups and non have been as hardfaced as this little cretin!!) Saying that, she sleeps under the covers with me, first time she did it I thought there was a rat in the bed as it was crawling up my leg!
(I nickname her Little Black Rat, as she's a Chihuahua!)