4 Year old Pomeranian started peeing on the carpet

In the last 2 months my 4 year old Pom Ariel started peeing on the carpet. She has never gone on the carpet before not even as a pup, if she had had an accident she would always go on the tile. Could this be a behavioral thing? A year and half ago my baby and I moved in with my mother and Ariel, unfortunately my mother passed away in December leaving me with Ariel. The first month she had terrible depression waiting by the front door night and day. After one month she snapped out of it going back into her daily routine sleeping in her bed, etc. Now my son is walking and the two chase each other all around the house having a great time. But I can’t tell if she is upset about something ether regarding my mother or the baby. Yesterday she went two times on the carpet I just don’t get it. Help what do I do?