Many, many *many* years ago, I taught my brother how to play RPGs when he was eight; while out working in the fields on the family farm. We used no rules, no dice, no character sheets, nothing, just taught him the concepts of role-playing by starting almost every scenario with, "What do you do?", as we walked the land.
"Where am I? What do I have? What am I?" would be his eventual trained response. I would put him through mysteries, strange places, or just wandering in a fantasy world with very little structure, but lots of interactions. Twenty years later we still game together and the phrase, "Put me on an adventure!" always brings a smile to our faces.
I would recommend avoiding, or extremely simplyfing, mechanics, and focusing on character interactions and choice making within scenarios. Allow her to customize her character as she plays and show her the make-believe aspect of RPGs as opposed to the rules just yet. I think that would be the best approach; her interest will kindle as she discovers the freedom and imagination of role-playing games.
IMHO.
I wish you the best of luck!