After using the resolution for MC-75547 by deleting the DIM-1 folder I had my friend get on my Lan World. Something strange was going on because my friend's skin was not rendering. When she got on she was at spawn with no items so she had to get back to where she was before where I restored her items by spawning them in. After several hours of playing we left and exited the world. When I got back on the world it was really laggy so I closed minecraft and reopened it while my friend did the same. When she got back on to the world she had her normal skin back but had the inventory that she had before she entered the nether a while back. All the items in her inventory were lost and I don't know how to restore them (because there were quite a lot). When I investigated the world file I found that there were now three files in the playerdata folder rather than the previous two.