min pin doggie

She's almost 8 years old.  She's getting more and more neurotic as the days and weeks go by.  They are a high-strung breed anyway, and when we first got her our vet told us to train her immediately as far as not allowing her to growl when someone was around her food bowl.  She said for me to put my hand in the bowl while the dog was eating to show her I was the dominant one.  I did that.  She seemed to do okay for a year or two but then started becoming really, really protective over her food bowl, and even her food bowl area.  We used to keep her bag of food in the same corner beside her food and water bowl (we keep it in a separate room now and sometimes she will sit in front of the door to that room and even lie down in front of it, as if she's guarding the area).  She got to the point where she was sitting beside the bag of food and would growl and become tense and nervous anytime anyone even just walked by the area.  She even went so far as to nip the ankle of one of my son's friends as he just walked by that area on his way to another area of the house.  We have tried locking her away in her kennel, taking the food bowl away when she growls, set the bowl back down, allow her to go to it, one of us goes near the bowl and if she growls we take it away and that process goes on until she stops growling when one of us is near the bowl, but it hasn't broken her.  Maybe we haven't been consistent (I know we did not, but the entire family needed to be doing this and I couldn't get anyone to be consistent with it besides myself).  She is getting worse and my main fear is that she might bite one of my children or a friend of theirs who may be visiting.  We've resorted to (usually) just keeping her pinned away in her kennel when friends are here but then she barks incessantly and we have to keep reprimanding her.   She also (when someone comes over) will go up to them and sort of jump up and put her front paws on them as if giving them a small push and appears to try to be dominating.  I've reprimanded her for that as well by putting her in her kennel when that happens.  I also tell my visitors and friends to tell her a stern "NO" and that usually helps.  I've only given the "highlights" here in this story.  There are smaller details (she bit my son's ear when he bent down beside her food bowl and brought blood), and other incidents.  We give her no table food whatsoever, only her allotted amount of dog food twice a day and water.  If anyone has any suggestions or helpful tips please do share.  Thanks very much.