Hi Edward
I have been training dogs for years, so I hope the following advice will help you. Sounds to me like the dog has a problem with you, not the other way around as you put it.
You have not said whether or not she does this with Iris as well? You have also not said whether or not she is normally clean inside when she is not excited? If she doesn’t do this with Iris, the ordinary treatment for submissive peeing wont help, and you will have to modify the way the dog views you, Iris, and her relationship with both of you. The dynamics of that will have to change.
Anyway, for now this is what you should. This is a two pronged approach which will not only treat the symptom, but also the cause. To treat the peeing.When you come home, don’t go inside. Open the door and call her out. Lead her to the area where she normally does her business, then acknowledge her. Pick her up and carry her as a last resort if she wont come, but a bit of encouragement should do the trick. Once she pees, praise her, and stay there till she is over the excitement. Then take her inside.
You will have to do this everytime you come home, but eventually she will get the message. Get Iris to do the same when and if she gets home first-whether or not she does it with Iris, she will still have to get the same treatment from both of you. Once she gets the hang of this, (the dog, not Iris)when/if she does pee inside, growl at her immediately and promptly get her outside, picking her up as soon as she starts peeing should do the trick.
The other issue you are having here, which I think is contributing to the problem, is her dependence on Iris, and how she views you in relation to that. You are going to have to get her over this, and the best way to do that is to have Iris ignore her when you are all sitting down together. As Iris is not responding to her demands for attention, you will be calling her, patting her, playing with her etc. Whatever rocks her boat. Do this consistently, and she will beging to feel differently about you. It could take a while though, depending on her age, how long she has had Iris to herself if she has, and a host of other factors. Be patient, but diligent, and only have Iris ignore her when you are all together and relaxed.
While not 100% sure here, from what you have written it sounds like you are either not really into dogs, feeling a bit left out because she prefers Iris, or something similar. Was the dog with Iris before you were, or did you both meet the dog at the same time?
Whatever it is, and you will know, you have to get the dog to feel like you want her as much as Iris does. Dogs are way sensitive, and if you are feeling any of the above, she knows already. Hence the behaviour. If two or more people don’t feel the same about a dog, the conflict can give way to sometimes bizarre behaviours.
You haven’t said how old she is, but if its not a case of the dog having Iris before you did, could it have started about the same time she started experiencing canine puberty. (the dog,not Iris) Behaviours like this are less likely if the dog has been desexed from a very young age, but that is no guarantee either.
So all you can do is to try the above, and keep at it. Persistence, consistency and repetition are the key to training any dog. It may take a number of weeks, but eventually you should see improvement.
I hope this helps you
Cheers