More than likely she's barking because she's tied the fact to doorbell=guests. Then she tied doorbell=barking=guests. In other words, she thinks by barking she has the power to make you open the door to get the person to come in. Try getting someone to ring the bell. DO NOT open it unless she's quiet. If she's quiet for even one second, open the door. Start to close it if she starts barking again. She needs to learn that barking will keep her from greeting the guests she's so eagerly to see.

Don't give her attention when she's barking. Nothing other than a sharp command to stop barking. I personally like "quiet" because "no" is used too often and its a word they learn to ignore (you already said she ignored no in this situation) Just say "quiet" once and wait 15 seconds before you say it again. Wait for her to settle down before you go into a rush of "quiet... quiet.... quiet... I said QUIET!" Teach her the quiet command on little things she already quiets on before you attempt to use the word on the doorbell. Once she knows it, then employ it on the doorbell.

Remember, in the beginning you'll also have someone on the other side of the door who knows you will be working with her, so there's no urgency to answering it until she settles down. As soon as she stops barking open the door, let the person in. Repeat, repeat, repeat with as many different people and at as many different times of day as possible. Its going ot take some time to un-train her in something she's done for several years now, so be patient and consistent.