I asked my girlfriend if I could run my fingers through her hair?

I told her he hair looks exceptionally beautiful today, "can I run my fingers through your hair". She blushed, smiled and said "yes". So I walked over and swiped my finger above her lip and said, "that's nice". She instantly got angry and won't talk to me now. Why?

I asked my girlfriend if I could run my fingers through her hair?
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