Are you joking me?
It would be a long and tender job: I would NOT open her pussy at all... Only taking the pussy lips between my mouth lips and would suck them gently, for long moments... going up and down, sucking the clitoris and the pussy lips, making everything wet wet wet, hot hot hot... I hope she enjoys tender but continuous sucking till she'd have her clitoris orgasm...
but if she doesn;t love this way... I would spread the lips apart to push my tongue deep before pushing my fingers into her...