How to gently break an obsession, help please!

[rogersmellyonthetelly]

My dog is obsessed with the front door. When allowed, she sits at the top of the stairs which face the front door, watching intently, and growling and barking at any sign of movement. She growls and mutters almost constantly, and at least once every half an hour she erupts into violent barking and runs downstairs to the door, hackles up. She also sits in her basket in the sitting room which she moves until she can see the front door, and then stares at it intently. If I close the sitting room door so she can't see the front door she relaxes and goes to sleep.
I'm worried that she is becoming obsessed with the door and windows at either side. When someone actually does knock, she bolts downstairs and barks manically until I answer the door, and if I don't restrain her she dashes through the door and starts jumping up and licking. She is very very friendly, has never shown any aggression towards people at all, strangers or otherwise, just desperately friendly to anyone and everyone at the door.
How can I stop her obsession with the front door, it's mainly the constant watching I'm finding worrying, and the annoying little chuffs and growls that are a constant. I don't mind her barking at someone at the door, but barking at absolutely nothing is getting ridiculous and happens all the time. She is so loud I can't actually hear if anyone is knocking or not, so I have to come down stairs to check, which will be a real pita when new baby arrives in a few months. Also can do without baby being woken constantly by un