The wood has split for sure. That is where the grain runs if you find a picture of a guitar with a similar neck that's not painted. If you can get a credit for her do it! I have repaired my fair share of these but it's never pretty. Lots of work to be sure. The neck would need to have the finish removed, more than likely the split exaggerated and then the joint set. It's not uncommon to completely remove the set neck and then reset the whole thing where the split occurred, then a finish reapplied. Once the damage is repaired and the finish restored, you are set! But as stated, lots of work. You rarely see cracks in finish that follow wood grain unless....... you guessed it.