It looks like it's a wound string, not solid. You can tell by the kink near the end and the fragment of winding sticking out. It could wear down plastic frets, but I doubt it would damage the body otherwise. From the picture, I can't even tell if they're even plastic frets. The color indicates metal. If they were plastic I'd expect them to be the same color as the fretboard. The light reflections on the body don't indicate any warpage of any kind. If it was, the lines would be distorted near the bridge. If it's as lightly used as they say, if I bought it to play I'd just change the strings and get on with it.