wait before tossing a stained book?

To make a long story short - on the 3rd I got a stained book. I asked for my credit back. The sender wants the book back but doesn't want to give me a credit for returning it. She wants to send a check, which I can't accept (I mean, I can't take checks). I told her that, and said maybe another form of payment? She hasn't responded yet.

How long do I need to hang onto this stained book? It's been a week since I told her I couldn't take a check. I know this sounds stupid, but it's really stressing me out.

How would you handle this? Thanks in advance.

The sender wants the book back but doesn't want to give me a credit for returning it.

I'm not sure I understand this.  She sent out a book that doesn't meet PBS guidelines, and is refusing to return the credit until/unless you return the book?  If this is the issue, why doesn't she just put some stamps in an envelope and mail them to you?  In any case I hope that you marked the book 'damaged by sender' not to be mean to the sender, but because that's the appropriate way of handling the situation.

Any way, if this is stressing you out, the easiest thing to do is send her an e-mail saying "forget it" and throw the book away and move on.  No point in waiting if it's bothering you.

You have to tell her the credit is due now since she broke the rules. Then give her 5 days to send the postage stamps for the book or another credit. If it's not sent within that time tell her the book will be pitched since you have no place to store it. Either way the mark will be on her record if you stated received damaged. Then you move on. I've had my share of water damaged books lately too.

I would offer the book as a freebie with an order from my shelf.  Unless it was stained beyond readability.   I have a feeling you are not going to get a credit back.  I hope you reported it as received with a problem. So at least if this is a habit of theirs then PBS can suspend their account.  I also agree that they are offering to send a check in hopes you will drop it altogether.  It only takes 10seconds to buddy someone a credit. And it would be cheaper by the time you factor in the cost of the check, envelope and stamp.  She's hoping you just give up. 

Thanks to everyone who helped.