This is an old topic, and I'm sure it has come up before...
What is everyone's theory on why Leia reminisces about her mother to Luke?
This is my take. Leia is force sensitive at this time, but doesn't realize it. In the Empire Strikes Back novel/movie (can't exactly recall,) Yoda tells Luke something along the line of through the Force, you will see friends and loved ones. Wish I could find the exact line. This to me means that you can draw upon images and visions of people using the Force. I believe Leia has this ability, and has done it with Padme, and because she is untrained in the Force, she mistakes them for memories.