Fridge / Star Trek The Next Generation S 7 E 9 Inheritance

• Data might not have made a decision of what to tell Julianna until she reactivated. Noonien told him that when she first opened her eyes and looked at him, she smiled and he knew she was really Julianna. When she wakes up and gives the same smile to Data, he realized that yes, she was the "real" Julianna.
• Data never actually believed she was his "mother" until holographic Soong was discovered in his head. He only accepted her initially to get more of her Back Story, to see if there were any hints she was some sort of Manchurian Agent or impostor. As mentioned above, he didn't even think she was the "real" Juliana til she smiled.
• Data insists that the jump from the cliff will be perfectly safe and virtually tosses Juliana off the cliff with him. Juliana breaks apart upon landing, showing that the fall was certainly not safe for a human woman, but Data had already all but confirmed Juliana's true nature, so his analysis of the fall's safety was apparently counting on her being an android. The fact that he didn't scoop her into his arms and make the jump for them both might even suggest that he wanted to use the fall to confirm her nature. (And Data may have meant "safe" as in non-fatal, as a human woman would have just had a compound fracture that future-medicine could easily heal.)