Aggressive 18 month old boxer

Question
Recently we took in a boxer whose family did not have time to spend with her.  She spent her days locked up in a bathroom or in their fenced in backyard. We have had her for two months now.  At first she was very protective of the house and aggresive towards all strangers.  Now she barks when people come to the door.  She soon settles down and will try to be petted by most company.  This is with the exception of my husbands best friend and my husbands father.   
   She simply grows at my husbands father and leaves him alone.  We took her to his home and she seemed to do better.  She is still unsure of him but only slightly growl with out any lunging.  She mainly avoids him.  
   She is much more aggressive with my husbands friend.  She will lunge and snarl at him and seems to try and conner him in the yard. It is quite scary.
    I am not going to quit having family and friends over to the house but I really am becoming attached to my boxer,  she is the best running partner, is great with my daughter, and is beautiful.  I don't want to have to get rid of her. Any help you could offer would be great.  
Thank you,
  Erinn Petsch

Answer
It sounds as though the friend and father-in-law are reminders to her.

They must remind her of her abusers. Yes, abusers.

If they "family" kept her locked up in a bathroom and in a backyard- and did not socialize her- then she was also abused.

It's quite possible these two men remind her of her abuser, and also, some dogs dislike certain people- the sense character and kindness. It's quite possible these two men are not avid dog lovers, and are the kind of people that will not spend money, time, effort on a sick dog...

I don't know- but these are factors to consider.

If she is good with you and your children, then there isn't anything "wrong" with her-- it's simply she does not like your husband's friend and his father.

The best you can do is leash her when they visit for a training period.

When she growls and displays aggression, tighten the leash and tug/yank it, reprimand her in a stern voice using simple commands-- and stay consistent always.

Within a few weeks of their visits and this approach- she will be calmer.