emotional responses

I have a student with autism whose emotions have been over the top lately - when she is happy, sad, angry, etc. - she is having a great deal of difficulty regulating her emotional responses. She is even reacting strongly when she is watching a movie or when another child is happy, sad, or angry. It is more than just imitating what she is seeing, she becomes much more emotional than the other person and isn't able to get back under control easily. Watching the sad part of a movie can leave her crying for at least an hour. Any ideas?
Thanks!

Ant: It is not uncommon for some children with ASDs to have very uneven moods, and be on a kind of emotional roller coaster. Some are prone to extreme irritability and meltdowns, and some have such severe mood issues that they may be diagnosed with a second condition (like Depression or Bipolar Disorder). Whatever the case, it can be a very difficult issue for parents and teachers to cope with.

You can read a short article about this issue under "Moods and Meltdowns" in the "Challenging Behaviors" section:
http://www.iancommunity.org/cs/challenging_behavior/mood_instability_and_meltdown