defiant urinating

Question
I have the most wonderful 7.5 yr old shih tzu. 'Baby' She is a spoiled rotten little brat that 'talks' with her eyes. She can communicate just about anything. I have had dogs all my life and used to breed min-pins (hence the name cherylpin).I got baby when she was 3 mos old. She is so devoted to me. She was successfully crate trained and graduated to being paper trained '. A few months ago she started expressing displeasure w/ me by defiantly urinating if I go to the mailbox, the basement w/out her. She'd leave just a few drops under my coffee table. I reprimanded her, reinforced 'use paper' and put her in an open 3x3 wire pen so she could see me but have no interaction w/ me. I'd ignore her for about 15 minutes and go about my business w/my other dog (shih tzu 5.0 years old). They are best buddies.
I'd let her out and make no comment. I praise the heck out of her whenever she uses the paper pad. Now she thinks she fooled me by finding a different spot to leave just a few drops when I'm out or downstairs. If I take the trash to the road, check the mail or just come in from work I have to check for her message to me before I positively greet her. She absolutely knows what she is doing. She is extremely intelligent & successfully trained for years. She isn't voiding in great amounts, just leaving me a 'mark'. She stil does her routine voiding on the pee pad. I can't actually catch her because it's only done when I'm not w/ her. I know it isn't the other dog. I purposely checked this out by occasionally bringing one w/ me when I was out of the house or downstairs. Sure enough it was 'Baby'. Now she know's the routine,I do a visual sweep.If there's no drops of urine she gets her regular 'I'm home' praise,. If there are urine drops, I scold her, remind her to use the paper and put her in 'jail'. I'm not sure how to curtail this behavior. I'd appreciate any advice you could give me. (she does not have a urinary tract infection and is not diabetic and has had no major changes in her life). Just a spoiled litte 9 pound brat that is a great part of my life. when I die, I want to come back as her! I hope you can help. Ive never had any behavior issues with either of them before. Sorry for the long winded note.  Cheryl

Answer
Better a long question than a short one the leaves me guessing, and perhaps not giving a good answer.  I do wish you would have said if she is spayed.  I think you are right, she is challenging your status.  That is less of a problem with dogs that are spayed.  If not, do so.  

It is unusual for a dog to suddenly challenge its owner at 7 years old.  Can you think of any changes in the household that would have upset her?  If the other dog is approaching 3 years old, or declining with age, she could be challenging it.  Start with obedience training.  The key to most behavior problems is approaching things using the dog's natural instincts.  Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm

Even with obedience training, she will have to be in sight, or in ''jail'' all the time.  You will need to learn to read the dog and learn its schedule, and when it needs to go out. Keep it in sight, closing doors and setting up gates. Some people even leash the dog to themselves. I have used a tie down at my computer desk.  If you catch it in the act, give it a sharp ''Ah, ah, ah!'' and take it out.  When you can't watch it, crate it.