Boxer / Lab mix agression

Question
Our 11 month old Boxer/Lab female was adopted at 8 months.  Previous owner had rescued her at 8 weeks from the pound.  Wonderful dog, very intelligent, very communicative but doesn't often bark, bonded with us quite quickly and is able to be off leash when outside with us in the country (we don't try this in the city except within the dog park#.   Aggressive around her food but not of treats #which she gently accepts#.  Previous owner gave her up after being bit. Obedience trained, submissive with other dogs and even puppies and toddlers, friendly will all strangers.  We do not crate her and she has displayed no overly destructive behaviour #just limited puppy mischief#.

We can work around the aggression linked to her food bowl at feeding times #and this seems to be diminishing), however, she is regularly growlly in a bossy way when she is very tired.  She likes to stay close by and will follow from room to room, but responds with growls if you stop to give her a pet.  

We feel caught - if we stop touching her, she learns that her growl is the correct communication to get what she wants - that is to be left alone, but when we continue to pet her, her growl will escalate and she'll start showing her teeth.  Although she appears very ferocious at these times, we are 100% confident that it wont lead to a bite and we often rub our fingers over her front teeth to show her we are not afraid.

It is easy to get her out of this mood with any distraction - a toy or treat, a new person entering the room etc.  However, she will resist any command when she is in this mood, except a very slow and reluctant sit.

This behaviour is increasing as she gets more comfortable with us.  The same pattern exists with friends - when they are first new to her, no aggression is exhibited but with time, the aggression appears.    

How would you recommend we respond to these bossy growls?  We are concerned others will become fearful of her and therefore it is important to stop this behaviour.

Thanks!

Answer
Since she was rescued from a shelter at 8 weeks old- she had absolutely no training, socialization, or anything from her mother.

This is absolutely necessary to socialize her, teach her what is acceptable, and what is not.

No one has. She had no litter or mom.

I have never heard of a Boxer growling at being petted, yet follow you around too...

....

Use a whistle when she growls and verbally reprimand her, leash her and take her to a "time out" area, whether a crate or a room closed off. The idea is to remove her from the family and let her know her behavior is unacceptable.

To re-establish you are "alpha" and not her, try this:

Put her dog bowl on the counter or kitchen table with food in it.

Place cookies or crackers on the table behind the bowl.

Set her in front of you to watch.

Eat the cookies or crackers without looking at her...ignore her.

When you are finished, place her food bowl down in front of her and tell her it is okay to eat now.

The pack in the wild do this: the alpha always eats first while the pack waits and watches. The alpha gives them the left overs if there is any, and tells them when they can eat.

Once this has been done for around 3 weeks, with the whistle and time out-- things should improve.


Also, if possible, when aggressive, physically push her down into a submissive position on the floor/ground, and hold her there for a few minutes until she is completely submissive to you.