I would leave the adult Heinlen books for later - fathers initiating daughters into sex might start conversations you don't want. There is also quite a lot of mild sado masachism and sexism. I like them but you do need a filter.

There is also homosexuality in the Pern novels. This would worry me no more than any other sexuality but you may disagree. The three about Melody, harper of Pern are usually recommended for younger kids.

I just read whatever was around by 12 so maybe just read the ones listed and work out a system for choosing from the adult shelves? I read a lot that was probably not suitable.

Has she read Watership Downs?