Well, first off straight shota is not normal shota. Normal, plain ol' ordinary shota is inextricably linked to yaoi, and the question was about shotas. Female straight
shota fans scarcely even exist. The handful who do are pretty much all bisexual/pansexual/tumblrsexual and are still using the shota as a self-insert in the pursuit of the warmth of a maternal figure. In the case of normal shota the model was Fahrlight, who identified with the shotas so much that she eventually started undergoing sexual reassignment to become Tom Hiddleston. In the case of straight shota, the lolcow profile changes to Nemu, whose sexual fetishes usually involved attempting to recapture the sense of comfort she felt when her mother tried to take care of her.
Another indication that female straight shota fans barely exist is that while high profile female perpetrator cases exist, none of them targeted males who fit any sort of shota archetype, whereas male predators often target a lolita archetype. Attached is a picture of the infamous Mary-Kay Letourneau and her 12 year old lover Vili Fualaau. Note Vili's relative height. Not visible in this photo but visible in others taken at the time he was 13, he had a few tattooes and visible muscles. Vili is not someone who would make anyone think "this is an innocent anime boy like Shotaro Kaneda." Neither are any of the other victims of real life cases of adult woman/younger male sex–almost all of whom are ages 16 through 18, not particularly close to Shotaro age. I spent a few days just watching true crime videos on YouTube once and a few of the ones that came up were about female teachers who molested male students. The female teachers all varied but the male students were more or less all the same; tall and well built athletes who were having serious academic problems. Family problems were not a factor in the male students' lives, the way they usually are for girls who get targeted by male teachers. The pattern of offense is different because the offenders are different. In at least two of those YouTube features the students described their social "problems" afterwards as their fellow males acting like it was a great achievement when the guys themselves felt broken up because their relationship ended. And that's it, that's all, that's the end. They weren't innocent boyos who were given a forbidden adult experience by an overwhelming authority or fully realized personality. They were physically adult men who endured nothing more severe than the trauma of experiencing a relationship breakup. The usual response to anyone who points that out is an argument that 17-18 year old men are not emotionally or socially developed enough to have ever entered a relationship with a 25-28 year old teacher, but given how miniscule the social centers of men's brains are it's doubtful that they are mature in that sense at any age at all. The women were not shotacons pursuing shota, just heterosexuals taking the opportunity. Then there's the opposite extreme, an extremely small number of women who perform opportunistic sex crimes on victims who are completely undeveloped and usually 6 years old or younger.
Opportunistic sex crimes are just as criminal as perversion-motivated crimes, but criminology and psychiatry separate opportunists from actual pedophiles (the first because the pattern of offense is different and the second because the medical facts are different). And all of the female sex criminals were opportunistic offenders, not shotacons. This points to a fundamental divide between female "shotacons" and male "lolicons" since only the latter commit sex crimes. It seems likely that the divide is that male lolicons sexually target the lolita archetype, and female shotacons sexually identify with the shotaro archetype.