[I assume that you meant the recent post in the thread about first contact with a client for this one, instead, so I'm responding here.]
So, what's the issue?
The client says
- you couldn't possibly have spent as much time as you claim?
- you spent too much time?
- you exceeded your estimates and she didn't realize it was an estimate and not a firm bid?
- it's about the time but it's really that she doesn't like what you've done or needs you to do more and it's easier to try to "get" you on quantitative issues than qualitative ones?
- something else?
Unless there's something going on that you're not describing it doesn't sound as if there's any fault on your part. Have you tried asking this person what she wants? If this is all a ruse to get a lowered price, I'd suggest holding your ground.
PS It did occur to me after my last post that if you're under 18 your signature by itself doesn't "count" on a contract.