Problem 1 : The urine odor. Try saturating the smelly spots with Natures Miracle or Odoban. Let air dry (keep windows open day and night), then have the rug professionally shampooed. Chem Dry comes to mind. Good luck. Problem 2. Regarding the behavior of the Nanny. My daughter is a self-employed nanny. She has plenty of customers because she is darn good and kids love her (and she loves them) . She is reliable, always on time, will clean up a little, make meals and feed kids, changes diapers, has her own transportation (Mom and Dad keep her car running, but she buys her own gas). Anyway, my daughter would never, ever have a pet. She owns a cat that lives with us (Mom and Dad). She had an apartment for a while but her cat remained with us. So, allowing a Nanny to even have a pet is OUT. Tell your sister to be very careful in her next hire. And my daughter's in New York, and not willing to re-locate, so I guess she's out.

Replacing the subfloor is the best way to totally eliminate the urine. Some have had success coating over the plywood with several coats Kilz primer. and then a good oil based paint. As long as your fastening and not gluing directly the paint encapsulation does work to some extent.

I second that advice. Buy a lot of nature's miracle and pour it on liberally; then let it sit in the carpet for weeks. Be patient. The enzymes in it eventually digest/break down organic substances like urine, poop, vomit etc. You can buy it online or at pet stores.

Joepyeweed is right. You have to give the solution a good long time to work. If you keep the area damp with the solution, it will digest the stain. I once got blueberry stains out of a white cotton shirt by keeping Simple Solution damp on it for three days. No sign it was ever stained. I have an almost-house trained dog, and another who is on steroids, so sometimes must go in the house. I first use my Spot Bot (or Little Green Machine - same difference) to suck up as much urine as I can. Then I soak the area with SS and let it sit at least a half hour and suck up the fluid (hoping to "wash out" more urine with the SS) and then I soak it again with SS and just let it dry. If it is a vomit stain or other difficult stain, I will cover the carpet with a damp cloth to make sure it does not dry too quickly. If you use any kind of machine to suck up this kind of spot, you will find that the machine soon reeks! I wish the instructions had said to rinse the machine several times before putting it away. I will suck plain water through the nozzle and hose, dump the container and repeat several times. The last time, I use it to suck up Simple Solution and then let it stay in the machine. Oh, how I wish I had done this from the start! My new game plan for dealing with incontinence is to cover the hallways (where the dogs "go") with washable quilted incontinence pads like they use underneath people in hospitals and nursing homes. I got them for my father-in-law originally, but found that they worked great for the dogs, too. They contain the urine and have a waterproof backing, so the urine does not get to my carpet anymore. My father-in-law lived with us and his caregivers were here all day. He died a couple of weeks ago and my three dogs are now alone most days. I have my sister stop by on her way home from work mid-afternoon, and she lets them out for me. On the few days that she has forgotten or my arrangements fell through, the dogs have been making it through the day pretty well. My almost-house trained girl is getting better and better. It almost seems that she is finally "getting" it!