Barking/nipping boxer when she doesnt get her way

Question
I have a 20 mo. old female boxer, Mia.  Great personality, wonderful dog, except for one thing....when you tell her 'NO' - she will bark at you, nip at your hand then jump at you!  We try to control the situation by being calm, walking up to her and getting her to back down without yelling at her but she will continue to bark, nip and jump and run around the come back at you.  It becomes a game to her until we are able to grab her collar and then she will lay down and stay til we tell her to get up.  But she will do it again later. when we let her out to pee she digs in our yard and telling her "NO" starts this whole thing over again.  Any suggestions.

Answer
And, when did this all start? At what age?

It didn't happen overnight.

The lack of setting boundaries for her at a younger age is a cause.

When a puppy is 2 months-4 months old, discipline needs to begin and boundaries set, what is acceptable behavior and what is not. Time outs work well with puppies...

...however, Mia is going on 2 years old and already established she is the boss and you are a plaything- not the boss; the alpha.

Are there other pets in the household?

Begin to establish you are the alpha... and any other adult in the household:

Take her food bowl and set it on the kitchen/dining room table or counter where she can see.

Place some cookies or crackers on the table behind the bowl for yourself.

Sit her in front of you to watch.

Pick up a cookie or cracker and eat it (them) without looking at her...pay her no attention except to make her watch.

When you are finished, place her food bowl (with dog food in it) down in front of her and tell her she can eat.

What this does is prove you are alpha. In packs in the wild, the alpha eats first, all he or she wants (usually a male though) and tells the pack when to eat if there is anything left over. They sit by patiently waiting until told.

When she acts up and misbehaves (unacceptable behavior) immediately drop her down in to the submissive position on the floor. Laying on her side, and when her feet go up some, and she relaxes, she is being submissive to you. Keep her held in this position for 2-3 minutes.

This established that the alpha (you) demand submissiveness from her on your command.

Then if she continues to misbehave, leash her and put her in a time out-- like a crate or room away from family. Isolation is rejection from the pack for unacceptable behavior.

Let me know how this goes in 3 weeks.