Soiling inside house

[CreakyKnees01]

My adult DD has recently moved back home with her 18month old lurcher. The dog is used to being here as we dog sit several times a week and has stayed overnight too.
The dog is walked and had access to the garden. She is never left on her own for more than a couple of hours.
The last 2 weeks have been awful with soiling in the house. Yesterday I got home from work, let her out into the garden, went upstairs to change and came back down to a pile of dog shit in the kitchen.
This is just one of several incidents and it is beginning to strain relations between me and my DD.
Any advice gratefully received

When you let her out, is anyone actually going outside with her to make sure she does her business?

I don't physically go outside but I can see from the patio door that she squats for a wee. She then came back inside and pooped.
She's soiling overnight too

Ah, okay.

Has her routine changed since she came to live with you? I have to admit it sounds a bit like stress.