It really depends on all the details.
If you did the site for free initially, and now she's planning on paying another designer for work, I would personally be a bit upset. I've had similar situations where I did work for friends for free to "help them get started" because they didn't have the money to pay me and get things rolling at the same time. Then they paid someone else to do similar work for them.
But then, I wasn't offended as a creative contributor -- I was offended that I was taken advantage of. So the scenario is probably different.
If she's paying you for your upcoming work, I'd try to avoid letting it get to you. It's perfectly natural to feel like your art has been rejected, but that's the nature of the business. For every site you redesign, there is another designer in the same position you are now.