Well, as I stated previously, I think it would be very easy. There are only two parts she would need to disguise - the lack of a paycheck and the lack of a location to really go to regularly.
The lack of paycheck would be easy to disguise, especially if she was never really contributing money to the family anyway, as it appears. KC never moved out of her family home. So if she was never expected to pay rent or part of the groceries or whatever, then she would never be required to demonstrate having money. Her paycheck would have gone to her very expensive nanny, gas money, and the occasional nights out her folks knew about. No doubt if anyone asked her to contribute any funds to the family, those were the immediate excuses she gave.
The lack of a job site to go to is easy to disguise as well. First of all, this imaginary job was once a real job at Universal, and her family may have seen her there or had other evidence that the job was legitimate at some point. This imaginary job was very fortunately mostly evenings, nights, and weekends, and evidently part time. So all she had to do was get showered and dressed, slip her lanyard over her head and march out the door and she had two great benefits - her parents wouldn't fuss at her for not having a job and she had 8 hours of free time. My friend who had a fake job did this for just those two reasons.
It seems to me that the biggest risk of getting caught would have come from GA or CA finding her at home at some point when she was supposed to be at work. She would have avoided that by calling them at various points during her "shift" while she was at home goofing around on the computer to verify where they were, and if whoops! they caught her, she could just say she got off work early or someone called and said they would take her shift, etc.
I certainly, in my teenage years, faked a couple of shifts at work to go do something else, especially when I was grounded and work was the only place I was allowed to go... (hoping my folks aren't reading this!
) I don't think I could have *not* said anything about being fired, but it seems like once she left that detail out, all she had to do was keep up the leaving and returning and the stories about work and the parents would have no reason to doubt it.