You need some buddies to help you desensitize her. Have someone come over, and have them approach the threshold where she starts to get upset. Praise her lavishly while they approach, as this may calm her a bit. Have the person throw treats in her direction, so she has to "Find It" and focus on something else. You want to keep her on the edge where she is uncomfortable, but not ballistic.
If she starts to freak out, clap your hands, say NO, and put her in another room for a bit, until she calms down. Then take her out, and start again.
If she shows improvement and stays calmer for longer, or as people get closer to her, make sure to treat and praise even more. Also, dogs find your back much less threatening, so you can try having your friend "back into" you -- this may help if she believes this person is threatening you. It may not have an effect if she is "resource guarding" you, but it is worth a try.
Repeat, repeat, repeat, with different friends if possible.
Good luck!
