We have a two and half year old Labrador Retriever who in the past couple of weeks has become apprehensive about the first floor of our home. Sometimes we have to use a treat to get her to come inside to eat a meal after a walk. For the past couple of days, instead of eating her breakfast, she just goes upstairs and lays down next to me on the floor and goes back to sleep. She is very clingy to anyone who is home and tries to sneak out the door with anyone who is leaving the house. She is healthy, active, well behaved and we are concerned about her. When she is left at home alone, she goes up to sleep in our bedroom instead of sleeping in her bed on the first floor like she did three weeks ago.
Any suggestions?

Optional Information:
Type of Animal: Labrador Retriever
Pet's Gender: female
Pet's Age: 2.5 years
Name of Dog: Indiana

Already Tried:
Have tried to spend more time with her. Both my husband and I let her sit on the sofa if we are sitting there - or we have taken to sitting on the floor to keep her company. She isn't shaking or nervous - but she seems to be apprehensive about something.