This does not sound like emotional disturbance, and I would arrange an evauation with an Occupational Therapist to consider the possibility of Sensory Integration Disorder. If the behavior is a disturbance in class, it is OK for the teacher to tell her to stop and to place her in time out if she does not. I think you are making too much of an issue of what the other children will think. Children that age are very egocentric and her behavior will not have much of an impact on them.
Sounds to me like your daughter is seeking out sensory input with the pushing and she can't get enough of it or get it intense enough to settle herself. Try reading the book The Out of Sync Child by Carol Stock Kranowitz. I think maybe it will help you see other aspects if sensory integration you might not have considered. Disciplining and thinking she will grow out of it probably won't help. You can find the book at the library or search online. yahoo & babycenter.com also have groups you can join to findout more about sensory integration dysfunction a/k/a sensory integration disorder--good luck :0)