With most of the diaper WAHM's that I know....that would be very odd indeed for them to not accept an order from you just based on "she's a WAHM, she might copy me" suspicion.
So, either she's a really paranoid WAHM, or she has good cause to refuse your order, or you're reading something into her response to you.
I have many many diaper WAHM friends. We share a great deal with each other, including helping one another with designs & materials & such. But there ARE people out there who *will* copy someone's hard work, and that hurts a great deal when you are the one being copied.
Most WAHM's do reserve the right to refuse service for any reason. That is their perogative, and they do not need to tell you why they are unwilling to accept your order. It could be any number of reasons.