I am beginning to think vilters has a point on this.  If you drop the arms to her sides (eyeballing it) it seems that the nipples will line up at about top of her bicep.  I tried looking up some good natural photo reference and found a few that mostly all conformed to the mid bicep 'rule' but it wasn't very in depth as i have a family and it probably looked liked I was just surfing porn!

I'm not terribly concerned about it though, it seems to me you could morph it into line. spreading the stretch out enough as to not be overly noticable.  I'm not planning on many closeup naked boob renders anyway!