Is she swimming back and forth by the paper? Perhaps she is seeing a reflection, or trying to figure out what it is. Try removing it for a while and see how she reacts. Instead of putting backdrops behind my tanks, I just put decorations, that way there is no possible reflections coming from the backdrop that could possibly cause stress. My female LOVES it when I change out pictures, and trinkets behind her tank, she'll spend hours looking at them from every possible angle. When she sees me putting something new back there, she gets very excited and swims from the front of her tank and to the back, and front, like she's pacing, waiting for me to put the new decoration up. It's quite cute actually. Then when I finally get something put back there, she stops and stares at it for a long time, and kind of twists her body into different angles while she looks at it.