If you are in position where the camera angle is directed up 2B's dress, 2B will move suddenly and the camera angle will change. If this occurs ten times, the trophy will unlock. There are times when this might happen inadvertently especially when 2B is ascending elevated terrain. It can be done deliberately on level ground.
The earliest point where it can be unlocked is in the prologue right after you get control of 2B. You can do it immediately but it's particularly easy after you progress a very short way upon gaining control of 2B. There are some containers. While 2B is standing on the edge of a container, position the camera angle to look upwards under her dress. It takes a couple of seconds. When she abruptly turns, you know that it has worked. Do this ten times to unlock the trophy.
Note: If the trophy is too sophomoric for your tastes, it can be purchased for 50,000 gold in the secret trophy shop. This special shop becomes available after three playthroughs.