Continuity mistake: After Claire punches Peyton for the first time, there is blood on Peyton's face. When she gets up off the floor, the blood is completely gone.
Continuity mistake: The baby's burping pad disappears and reappears from Claire's shoulder after Peyton pretends to save the baby from choking on the earring. (00:25:50)
Continuity mistake: When Emma takes the baby to hide in the closet, you hear him frantically screaming. As they show his face, he is just looking around calmly. (01:41:20)
Continuity mistake: When the doctor examines Claire's breast, the robe around it changes positions between shots.
Continuity mistake: When Peyton meets with the lawyers regarding her husband's death, her glass is filled with ice in the close-ups, which disappears in the wide angles.
Answer: The same way any common criminal gets in to a house, she "broke" in by either kicking the door, or smashing a window, etc. A locked door is not that hard an obstacle to overcome.
Jazetopher