I'm a large 12, can I return it?

I sold a wetsuit, described as S/M, which is up to a 12 according to the manufacturers website. My Mrs is a 12 and it fits her, so should be fine.

Had a message, can I return it, it is too small! It is a 12, I am a large 12. How big is a large 12? 14, 16, 18? Anyway, I accepted the return. Just re-sold it, my instant thought was, I hope this one isn't misguided about her size.