One time was when she was 7, but
@mrken12 said he caught them changing it from 17 to 7 and the other time she talked about was when she was 13 and her sister was 7
I believe it was genuinely a typo. This story is from her book which is in publication. They wouldn't change it online all willy nilly like that.
Regardless, like you and others have pointed out, this wasn't an isolated incident. Lena recounted a couple incidents to illustrate how 'quirky' she is/was, but it seems this was modus operandi for her growing up. It is normal for kids to cross some lines as they learn about sexuality, but she was clearly a habitual line stepper...she and her parents ain't shyt.
She's a sick b*stard for her reaction (glorification) to it now, and she's a sick b*stard for the acts themselves.
Side bar: her sister was being molested growing up, her parents knew (or should've known) and did nothing, then grew up into a lesbian? The "evil right wing" is on cloud 9 right now