I asked about the thyroid because you mention that she has been on medication for the last 11 years and it is very odd to see a cat develop thyroid problems at 2 years of age.
I would also give your vet a call and make sure more then a CBC was done. A CBC does not tell use anything about the organ function and we would really want to get a full chem to make sure the kidneys, liver and glucose levels are all with in normal limits as these are the top three medical causes for this type of behavior.
That said I suspect this is related to you going back to work. This is not at all uncommon when there is even the slightest change in a cats routine. Cats in general do not do well with change.
The Feliway is a great product but she may need a few other things to help reduce stress and anxiety.
I would try to get a pheromone collar so that she is exposed to the pheromones on a consistent bases rather then just when she is in the room with the plug ins.
Feliway has these however we have been using the NutureCalm collar. Click here
* Composure treats are also helpful to reduce anxiety Click here
* Some experts will recommend Rescue Remedy but honestly we see little effect with this in cats Click here
If she is a cat that likes to play I would consider getting some interactive toys that can play with without you and or ones on times she can use when you are not home
I am going to give you a list of toys that we have found work great for these cats.
A laser pointer works great for this . They even have hands free lasers for cats as wellClick here for a hands free laser
Other toys that work well are the panic mouse and or a remote controlled mouse.Click here for the panic mouse
Click the links below for other toys that will get her moving Link 1Link 2Link 3 Link 4Link 5
Timer controlled.Link 1Link 2
It is also possible that this could be related to Feline Cognitive dysfunction.
This is similar to dementia in humans and can cause loss of training habits and cats may urinate and or defecate out of the box. There are medication that can help with this Click here
The natures Miracle is great. If you find it is not working I would try a product called Urineoff.
As a last resort prescription medication may be needed to help modify this behavior. One of the most common drugs we use is Amitriptyline. Click here
I hope this helps give you some other options to try to stop this behavior. Please reply back if you have additional questions or concerns and I will be happy to continue.