I know lots of women like this... is nothing strange. My first girlfriend was like that in fact.

Give her lots of time, maybe lick her while she is reading erotica. Let her know it's okay to take over if she feels she is getting close to orgasm. Also, some women get "numb" with too much clitoral stimulation, or if it is too much pressure. Maybe see if a lighter touch might work.
Hope this is helpful. Tell her lot's of women have this problem. she is lucky she can discuss it with you.

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If you won't listen to reason, there's always... Towanda!... Kathy Bates~Fried Green Tomatoes