messyjess - As a former teenager who was REALLY good at making up stories on the fly to smooth things over with her mom, I think you are probably right on the daughter "not being so innocent" train of thought. I might even question the validity of the "36 explanation" you were given. The first thing I would have done was try to think of a story that would play to my mom's heart strings and try to garner sympathy. I'm not saying she is lying about it, but it does smell fishy to this former teenage manipulator.
And the location of it is also a little strange. Why would she want to remember her dearly departed friend every time she looks at her "bikini" line?
Hopefully, you guys will be able to laugh about all of this in 20 years. Thank goodness it was something tiny!