Train her to have a "spot" when she hears the doorbell ring. Make sure it is out of the way of your incoming guests.
She must stay in that spot, quiet and calm until your guest are ready to greet her. She only gets to greet them when she is calm though.
This will take a lot of practice, since the doorbell is always so exciting! Lot of treats, and I would suggest a clicker to help train. I just picked one up from our petstore for a few dollars, and my dog picked up on it right away. WE love it!