I was thinking about that. I know we've only heard her side of the issue but I imagine it being something like this:
Nancy left on Saturday, June 28 for a vacation with her family. Since nothing was mentioned I would assume that she got her $300 allowance on Friday the 27th. So she is on vacation from the 28th until Sunday, July 6th. When Friday rolls around Brad might have told her that he wasn't giving her the money since he had given her the money for the previous week but since she was on vacation, she didn't use it for the family home. In this scenario she would mention needing that money for her vacation to which he would say she had her own money for vacation from the painting job.
Based on the timing of everything, that makes the most sense to me. Under the circumstances with the separation/divorce hanging over his head, I just can't believe he would suddenly deny her money for household needs.