Shopaholic and Sister - Sophie Kinsella Break, break, break it down now.

Jess, while originally as annoying and boring as Becky felt was quite a good eventual addition to Becky's life.

Luke got super annoying. Becky is a shopaholic, you are a workaholic. These people need to learn some self control.

Anyway, this has been my favourite shopaholic story so far. It was a bit less repetitious and Becky was slightly more likeable. I still found her ridiculously annoying.
Either way, this series is pretty addictive and entertaining even when I want to throttle the main character.