Help! Toddler escape artist!

Ok so my 2 year old daughter has figured out how to get out of her room in the middle of the night while my husband and I are asleep. The last two mornings, she has broken down the gate (quietly) and walked upstairs to the duplex to where my parents live (we share a duplex). My husband has been sleeping on the couch by the front door in hope that he'll hear her if she tries to go outside while I sleep with our 5 month old son. But she's so quiet! I don't know what to do because I don't want to lock the door on her...any suggestions??? Completely at a loss...

Also she wont stop unplugging and plugging in her fan (we live in a tropical climate with no AC). I'm just beyond anxious....