Fiona needing to borrow from her trust fund for the winter carnival

This was a girl who spent $8,000 on a credenza and boots at the drop of a hat. It seemed like she had all the spending money in the world, so why would she have needed to ask for trust fund money to pay for carnival rides? I know the obvious answer is to advance the plot and reveal that the Coynes were in financial trouble, but it just seemed silly.