It would be tempting to say that an observation couldn't hurt, but depending on who the specialist is and what the school is planning to do with the information the specialist presents I think it could lead you down a path you don't want to go, specially if there have already been problems with them labelling her.
I agree that you need to find out as much as you can about the specialist, but you also need to find out how the school intends to use the information from the observation. What do they see your role as being in all this? What happens if they want to put something into place that you don't agree with? Could you bring your own 'specialist' in?
Most likely the school has the best of intentions, but this type of thing can snowball if you don't make sure you are clear on the process and involved at every step.
