Rororro!

Rororro! manga summary: Chitose Morishige is a 12-year-old seventh-grader without a friend in the world. Her father, Professor Morishige, built a robot companion for his daughter to ease her loneliness. The only problem is that Ichika Robata, the android, is so lifelike that Chitose believes she's a normal human girl who either ran away or was kidnapped by her father. Ichika attempts repeatedly to prove that she's a real robot, with hilariously disastrous results. Published in Weekly Shounen Champion.