I recently found out via fark.com that there is such a thing as Nipple pinkening cream
to turn brown nipples pink. The example on the box showed a dark skinned asian girl with befor and after nipples origanel brown, and then pink as a non abortion having white girl. Anyway it was totally hot, but my point is this.
She could have had an abortion and used nipple bleach to cover it up (the scar another way also depending on how big the baby got)
If you find nipple bleaching kits in her medecine cabinet it should be a good tipoff she's covering.
food for thought.