I send a book to the address it said and it got return to me and I sent a message to the person and she said oh sorry that's not my address, and she still has the wrong address on the site. Should I ask for a credit?

I'd certainly get in touch with the PBS team and forward the PM where she says that.  Tell them what you just said here.

Ruth

Yes, definitely use the "contact us" link at the bottom of this page to send a note to the PBS team about it.  Copy/paste that PM from the other member there although they can see the PM if they want to.

I found this over in the Help docs:

It is the requestor's responsibility to provide a correct, dependable address to senders.

• If you make an error and provide the wrong address, you should correct this as soon as possible, using one of the methods above.
• If the book you requested is returned to the sender because of an incorrect address, the sender is not obligated to re-send the book to you.
• If a requestor uses a nonworking address to request too many books, or makes this mistake too many times, this can jeopardize PBS membership.

Looks like you don't have to re-send them the book.  It'd be nice, since it was their error, if they gave you a credit for the postage you spent.  Doesn't look like they have to though.