I dunno, but if you're an adolescent girl and find out how your peer group develops an overt interest for the other sex while you remain kind of distanced about the whole thing, then JJ's metamorphosis is perhaps not so surprising and planned after all. Reads more like your typical coming out (and of age) story. I haven't been in the situation, but being gradually confronted with the insight that you're gay and most other people aren't must have a devastating effect on your adolescent self confidence - we're talking about a mid-seventies middle-class US background here.
Jackie, otoh, was always the prom queen among The Runaways (and positioned by Kim Fowley as such, I even remember an article in some teen mag where her excellent grades at highschool and how she wanted to study were touted), she gets to go out with the handsome hunk from the school football team. Cherie had the trailer-park-trash-meets-Ziggy-Stardust appeal, Lita was the curvacious sex bomb, but All-American just the same, Joan the sulky Suzi Quatro lookalike that crossed over to the punks, Sandy was just a regular "guy" who you could always present to your mom without worrying and Miss Fox was the slightly aloof "I really don't belong in this here and have other plans".