Hello, my name isXXXXX and I have over 20 years of experience as a veterinarian.
I know that submissive urination is a frustrating problem, especially when it comes and goes as it seems to with Maya. It is likely she is responding to your boyfriend's body gestures, facial expression, or even his pheromones on the days that she submissively urinates. He may not even realize it but for some reason on those days she perceives he is stressed or upset and she wants to make sure that she is no threat and is doing so the best way that she can.
In the canine world this is done to show other dogs that she is submissive, they are in charge and is a great way not to get beat up if there's any doubt on the other dog's part that she is a threat.
Many puppies display this behavior but it tends to lessen significantly when they mature. In anxious dogs it may never fully go away.
Please don't discipline her for this behavior as it only makes it worse. She is already fearful and trying to show your boyfriend that she knows he is in charge, by yelling and getting upset he will increase her fear and confusion and decrease her self esteem further.
I recommend starting by ignoring the behavior and her when he is excited and when your boyfriend initially comes home. Try to have her outdoors when he comes home, let things settle down and then have her come in. He shouldn't talk or look at her directly and we need to make sure she's been out to empty her bladder. When she comes in he should ignore her, let her approach him and then she can have a treat from him for sitting or laying down. We want her to be less stressed and excited and see his coming home as a positive thing. By letting him decompress when he comes in he can greet her calmly. I would not allow her to ever be on furniture without being invited up with you or your boyfriend. She recognizes that furniture is something for the higher placed pack members and being on furniture when he walks in could be perceived as being pushy, and she doesn't want him to think that, thus she urinates.
We also need to work on increasing her self confidence. Obedience class is a
wonderful thing. She will learn what pleases your boyfriend, get rewarded for it and learn to trust him and that if she does what he'd like she is safe and won't get into
trouble. She also learns to do this in front of other dogs and people and may make some new friends which will also increase her confidence.
It helps for her to learn "sit" and "lie down" commands with a long stay as those positions make it more difficult for her to urinate.
They also give her something else to think about (following the commands,
looking to your boyfriend to see what is next).
When they are done playing rather then have him approach her he should call her to him, have him tell her to sit or lie down then give a treat and release her. That tells her that her work is done and play session is over.
If this is happening with company it may help to have her outside or in another room when company comes. Once the excitement is passed and everyone is relaxed and seated then have her greet everyone. Ask your visitors to ignore her initially while she explores and becomes comfortable with new people.
This pup is one that needs positive reinforcement, reshaping behaviors by rewarding positive behaviors, ignoring of bad behaviors and never corporal (physical) punishment.
Best of luck with your girl. She sounds very sweet, she just needs some self confidence.