How do I respond to non-Catholics arguing against the priesthood?

I have a friend that told me it was not necessary to be married by a priest, confess our sins to a priest. She is very versed in the bible and told me that it does not say anything that a priest has to be present for these things. Priests are just mortals. She said priests did not come about until long after Jesus walked the earth. I said the disciples were the first priests and St. Peter was the first pope. I was not sure how to respond to her to defend my faith. How would you respond?

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