I don't want to promise you results as sometime a fearful dog will never get over that fear. However there are things you can work on to help with the fear and aggression and controlling her behavior. It does appear to be fear based since she doesn't confront the person until they are not facing her. In addition, usually people are leaving when they get up and move away so she nips at them and then leave so she thinks she is causing them to leave thus it reinforces the behavior.
She needs obedience training. This serves multiple purposes. The first is that she gains more self confidence with obedience training. As she learns commands and what people expect when they say those commands she becomes less fearful of the people and more confident. In addition, obedience allows you to have her sit and stay until your guests are seated before allowing her to come into the same room where you will command her to sit and stay once again. Since she is trained she will sit and not be a threat to your guests.
They can also help her gain confidence around visitors including men it you allow them to also give her simple commands and then reward her with paper thin hot dog slices. Dogs usually work for these types of treats. The following site is helpful in helping owners train their dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
Bat training may also help as well.
Keep a leash on her at least at the beginning to give a short tug to get her attention off the visitors and on you where it belongs. If she growls or attempts to lunge in order to nip, give the tug and a firm low toned "NO". I think you will find obedience training and the other techniques will help her become less fearful of strangers and lessen any liability as well.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.