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Chances of her getting pregnant with this alone are near zero
For all practical purposes nil
It is possible to get pregnant by precum if you have been having intercourse.If you have just a drop of it on your finger and you insert it in her vagina chances would be very small but not zero.If you have been wearing clothes it is certain that you would have wiped the finger tip onto some cloth and lost the precum .After that if you insert finger in vagina for 3 seconds it should not cause any introduction of sperm into her vagina.
Have a good worry free day