Female Fighting Boxer

Question
I have a 1 yr old female white boxer (Sheena).  I have always owned boxers, and always males with no issues. We would always let her know what was ok and what was not, and when she got out of hand, we would lie her on her side until she would submit from 8 weeks old and growl like her mom and tell her "no" in a growly voice and she would always obey.   At about 6 months old Sheena began to have little tiffs with my other female boxer who was about 2.  I would make a loud noise and tell her no, and she would stop right away. HOwever these got worse and worse to the point where yelling and making her submit did nothing.  My husband and I began having to break up fights that resulted in bloodshead.  We had a behaviourist come in who did nothing for us honestly, and a fight even broke out with her here.  We made a painful decision to rehome our other boxer who is now a happy girl.  We kept sheena and we have a male who is 1 1/2 yo.  She will sometimes get to irritated with her as you can tell by her tone and I will tell her "hey" "No" and she stops right away, however I have had serious concern on bringing her around other dogs, especially since when I do bring her on walks and we encounter other dogs, she will stand still and stare at them, never lunges or anything but never wags, tries to smell or anything.  I try to touch her or snap her leash to bring her back and not so focused, but I do not know what else to do.  My dad lives downstair and has a boston terrier and today she went at her over a treat.  I have a 4 year old son, who she will give her little snap to, not to bite first but a warning so to speak, but I am concerned.  Can you recommend some things we can do with her to help this situation?  We like to go on walks but are worried if we encounter an off leash dog, which we have not so far.  At a recent walk another boxer on leash went after my male who didnt care less, but sheena was on for the fight, I had to drag her away and when I tried to calm her she latched onto my forearm, not hard and opened right away, but nonetheless did it.  I dont want my son hurt and we keep him pretty much away and leave her alone unlike my male.  I would appreciate any suggestions you may have.

Answer
The way to solve this would be to muzzle her and let her meet a lot of dogs ,as she can get used to other dogs and see they won't hurt her,and she can't hurt them

Also you can muzzle her in the yard with your other dog,for the same reasons

I have used this on a number of dogs,and has always helped,after a few weeks you can try her meeting other dogs without a leash