S.W.
I've never been able to bring myself to lock my kid's doors. Just seems to me like that would be scary. She's also got to learn that while she can come to you when she really needs you, she has to respect the sleep of others. This is the age where I got serious with my son about his very early morning wakenings... told him he must stay in bed or his room quietly until I come to open his door (after 3 1/2 years of being awakened at 5:30). He got it too... I don't think it's a bad thing to be harsh with her. Maybe you're not being harsh enough. She's got to understand this behavior is not acceptable. Provided she's feeling better, I would sit her down, tell her the rules. She doesn't need tickets to mommy... she can just get up and turn on all the lights and there she is. Maybe you could try taking away something important to her and she has to earn it back by respecting her family's sleep. Maybe Daddy should be the one to put her back to bed... is he more stern? I wish you luck.