I don't want to meet my girlfriend's father who molested her
Is the reason you don't want to meet him because he molested her?
Yes, and he is still molesting young girls.
If you know that your girlfriends father is currently molesting young girls then you need to turn him into the authorities. Your girlfriends father is breaking the law and destroying lives and if you are quiet, you are also guilty.
I'm thinking of turning him into the authorities.
That would be the best plan of action, since child molestation is a very serious issue.