A.B.
Hi I.--
When my 12 month old was afraid of the ocean, I brought his favorite ducky (bath toy) and plopped down on the sand near the edge of the water where he felt safe to play. Needless to say, every so often the water came up to and around us and ducky, but he was so busy playing he paid no attention. Once when ducky started "swimming" out he started to chase her in the water. No more screaming, no more fear. Today at 8 years old it is impossible to get him out of the water.
Soooo...is there an elevator near you that is minimally used and big enough to feel like a room, and that you are able to disable for a few minutes to allow you to have your twins play in it for awhile before allowing the doors to close? It would need to be a slow, almost imperceptably moving elevator.
Maybe in your church/synagogue, or some other place that is more quiet during the weekday. You might even first use a room that has a sliding door to close and open, and make a silly ding dong sound when you close it. Make a little picnic with her favorite yummies to eat and her favorite toys with which to play. She's still very young and desensitization should work pretty easily. If not, seek professional help from a child therapist before it gets to be a big thing.