Some councils have a weird definition of who lives where.
I had to pay for one lodger, September to March, but he worked offshore and because of lockdowns and things ended up only spending two weeks in my house over that period, but because it was his only home I had to pay for him for the full six months.
My other lodger still officially lived at his parent’s (something to do with where he was registered to vote) so I didn’t have to pay even though he was here all the time.
Scottish Borders Council if that makes any difference. Seems a mad system. Worth asking your council what they define as your home and her home.