I just found out my gf used to date her dad
Did she tell you something?
Yes, she told me about it
It's wrong to date family members romantically, as this can cause health problems in any offspring.  However, as long as their relationship is now over, I'm sure you can be happy with your girlfriend.
My gf is now with me and nothing more happened with them. We love each other very much, she can't get enough of me.
I'm glad you accept her past and you two are in love together.