Our dog Penny is 6 and a half months old. She's very smart, already knows sit, stay and come, is no longer mouthing and knows the difference between "down" (don't jump up) and "lay down". She was house broken almost immediately, about a month after we got her. The past few days she has gone back to urinating in the house! She does it in the living room and it started a few days after we got a live Christmas tree. Is she confused and think the tree means she can potty there? We are losing it! Everyone keeps telling me to put bells on the door so she can tell us when she needs to go out. Is this the best solution for her? Any info is greatly appreciated.

Bells hanging from door knobs has always been my favorite so yes do that. However, she may be confused by changes inside the home, tree especially. Either crate her or supervision 100% until the tree comes down. During the meantime you should also go back to initial house training approaches of frequent walks, praise when she urinates outside and quality treats.

Thanks, we'll get some bells and see how out goes.

Ok on the bells but crating and training are the key.