What should I do...is it aggression or dominance?

Question
I have a 1 1/2 year old GSD Cody.  She is a great dog.  Wonderful with all children, passed training.  Only aggressions I have ever seen are with people on bikes, she will bark and bark until they pass by.  She also barks when people come to the door, but will stop once i tell her it is ok.  

Now to the problem...I have a 93 year old grandmother who lives with my parents (since 11/05).  She doesn't like Cody, but tolerates her.  They will play ball together and my grandmother will pat her head, but she feels dogs belong outside, as all animals.  About 2 months ago when i went to give my grandmother a kiss goodnight, Cody stood up and started to bark aggressively.  I grabbed her collar, told her enough and to sit and she did.  It happened another time about 2 weeks ago when my kids went to say hello to her.  Then, this is what I am really concerned about since I think it has turned to the next level, this past weekend we were all up at the family lakehouse, my family including my parents and grandmother.  Cody must have snuck off.  She jumped up on my grandmothers bed and urinated.  She left her ball as to say, well..you know.  What should I do to make sure this doesn't escalate into anything more aggressive?  Do you think this is aggression or trying to prove she is dominant?  Any insight you can give me would be greatly appreciated!  I don't want to ignore this and then have something horrible happen.  My gut says Cody is trying to show dominance and not aggression, but it may be me living in a rose colored world instead of seeing my dog's true intentions.  I just can't figure out where this is all coming from.  She has never done anything like this before.

Thank you!
Carrie Ruegger

Answer
Hi Carrie,  normally when a dog goes to the bathroom on someone's bed it is to show dominance or basic disapproval with that person.  Normally we have that person work the dog in obedience so the dog begins to understand that that person is higher up on the heirarchy ladder in the family than the dog.  Unfortunately in your situation, a 93 yr old woman shouldn't be working a GSD.  I would have her make the dog do obedience while playing ball though, like making the dog stay and wait while she throws it, and then make the dog come after fetching the ball.  When the dog comes back, she needs to make him sit, and then hand over the ball.  Any obedience commands she can use would be great in this situation.  Hope this helps,

Dawn