Transferring WHV to tourist visa via re-entry

Hi,
I have read similar questions to this but not one exactly the same circumstances.
My daughter is in Japan on a 6 month working holiday visa and has been working and travelling in Okinawa for 4 months. She doesn't want to work any more and only wishes to travel for the remainder of her time in Japan. She wonders is it possible to re-enter with a tourist visa by exiting the country and transitting via south korea, returning on the same day. The benefit of this is the cheaper price of assorted rail passes which are not available to her while she is on the whv. She does not intend to stay in Japan beyond her original visa date and is not looking to extend her original planned time in the country. A prior post suggested a person would need to leave the country for"a couple of days", does anyone know if there is a specific rule for this, or if it is enough to simply depart the country and return, regardless of time frame. I do know that the WHV is a single entry visa so would no longer be valid on her return, but is there a chance she would be denied entry as a temporary visitor? We are Australian and are eligible for 90 day temporary stay entry without any visa application.

This seems to give you some idea.

http://www.japan-guide.com/forum/quereadisplay.html?0+94003

To make it sure, you'd probably better contact here.

http://www.au.emb-japan.go.jp/