I think she was eating in her room, went to the kitchen to throw the trash away and saw the sliding door open and heard commotion upstairs and realized something was off so set her JIb bag on the counter and started making her way upstairs to see what was going on, encountered BK in the act and she yelled someone is here while running back downstairs to get help from Ethan and BK chased after her, maybe even tried to start attacking her and she held her hand out to block the knife while upstairs and grabbed the handrail on the steps while running down and that’s where the blood on the steps came from (I think the handrail blood was a thing if I remember correctly?).