Hi there,
The first thing i would encourage you to do would be to start training your dog where to toilet again. This is probably the last thing you wanted to hear but it is the best chance to fix the problem. Some dogs lose their training and need to be reminded of what is expected of them.
Once you have started the training again here is a plan to reprimand her for toileting inappropriately.
The next time she has an accident inside:
* Growl as she is doing it. You must reprimand your dog as it is performing the undesirable behavior, because dogs only ever associate your punishment or reward with the very last action they have performed.
* Soak up the puddle or pick up the waste with a sheet of newspaper.
* Then clean the spot with your odor neutralizer.
* Keep the soiled newspaper, place any solid wastes or the soaked paper outside, or wherever you want their bathroom spot to be. This will give your dog a place it can return to that is marked with its own scent and therefore safe to use as a bathroom. (keep in mind that dogs mark their territory and therefore claim their dominance as they eliminate, if another dog has been where you want your dog to go, your dog will only go there if it is of a dominant disposition and wish to challenge the opposing 'dog'.)
* Take her out every hour (when possible) to that place where you have placed its waste. Introduce the command "Be quick!....Good Dog" as she goes and reward it her treats if you wish. This command is handy, as she quickly associates your voice command with the act of eliminating.
Another important thing to remember is that dogs are very much creatures of habit. Dogs like to toilet first thing in the morning, after playing and eating and before dinner. You must preempt these situations and take her out to toilet around these times. This will help take some of the guess work out of her training. Also when you take her outside, make sure she goes toilet before she is allowed inside again. This may mean you are outside for some time early on in training.
Occasionally there is a medical basis to inappropriate urination. Infections of the bladder are more common in female dogs than males and what may lead you to think that this could be the problem is if she is going more frequently than normal, and only producing small amounts of urine each time. The urine may also be more odorous than normal.
It sounds like your lab has a more behavioural problem than a medical one, so I would try the training first to see if you can get her back on track.
Be patient and good luck
Kate