So, what should she do if her parents refuse to remove photos, including her "sitting on the toilet or lying naked in my cot"?
You're telling me it's "absurd" for her to sue, and she should "Grow The Fuck Up (tm)". But you're not telling me what she should actually do. What choices does she have other than suing?
Easy, she should post 500-odd embarrassing pictures of her parents to Facebook, make sure they are all properly tagged, and then wait for her parents' offer to mutually destroy all pictures.
On a more serious note, I find it sad that her parents value their social media status higher than the well-being of their daughter. If she doesn't want the photos online - whether she was sitting on the toilet or on a bench under a tree - her parents should respect her wish. Those who say she should "Grow The Fuck Up" should note that this is exactly what she is doing: Talking to her parents apparently didn't work; short of hacking into their account or taking resort to violent means, suing them looks like a "grown-up thing" to me. I'd never have done that myself, but then my parents are sensible persons that would never have put me in such a position.