Most people who order a large print edtion really need it and would ask for their credit back if they received a regular editon instead. I would not send it unless you are ready to have to return the credit when they receive it.  Elaine

Well if you chose Tues by the mail by date then you actually have 2 days after that. It should say the date that you must mark it mailed by on the Books to Send out tab.  So you have a couple more days to wait for an answer.  I would cancel if you don't get a response. You'll lose your place in FIFO but since the book is posted wrong-it needs to be removed from your shelf anyway. 

When you post books you are supposed to use the ISBN that's on the book, not one already posted that looks like your book.  If she doesn't want it or you don't hear from her-repost the book w/the correct ISBN.  If it has no ISBN or the one it has brings up a different binding-then you need to post it w/o an ISBN. 

I would cancel the order and take the book off your shelf and repost it correctly.  Most people requesting large print need large print and this is the one case PBS will make you return the credit.

You caught it just fine, so you get to retain your "good person" status. :-)  Most likely she wants a large-print version.  There's no harm in waiting a day or two to see if she responds to your PM, though. 

I agree -- if you do not hear from her in time specifically saying it is okay to send, cancel and explain (with apology)  in the comments section that you made a mistake when posting the book.  It happens to all of us at one time or another.