My toddler is scared to sleep on her own?

Sometimes, some gentle exposure to what scared her might help. If she's usually not afraid of the vacuum cleaner, maybe you could buy her a toy one, and do the vacuuming together. As for the current behaviour, I agree with a previous post, this is just something you're going to have to ride out. Maybe you can put a chair in there, close to her crib, and every night, move it a little closer to the door until, in a few days, you're outside and she's quiet. Make sure that she has a night light in her room that will show anything that might be a source of worry or fear for her, and make her crib a safe and comfortable place at night - some toys, a comfort item, even a photo of Mum and Dad in a baby safe photo frame. It will get better, but you do need to be strict with her and make sure that she stays where she is. After bedtime, make sure that the house is relatively quiet, no more after bed vacuuming! Try, instead, getting your other half to take her into the garden or out for a short walk after dinner so you can get the job done without getting her worried. My son's 3, he still HATES the vacuum cleaner and runs whenever it's pulled out!