if sexual exploitation isn't her thing, It probably will never be...
figure out why she is not sexual, past issues, how she was raised... Try to address it.
more then likely she is not sexually because she doesn't enjoy sex or can't really orgasm or doesn't understand her body.
Focus on teaching her about her own body. Make he a squirter, etc... That's about the practical way to enlighten someone.
anyhow it all comes down to her personality, if she is generally not open minded, thinks her way of doing things is always right, sex is not a priority in life... It probably will never happen...