W.T.
I don't have a daughter, but I remember my first visit.
First of all, my parents were super open about everything, so I had a really clear understanding of how the body worked and periods, etc.
I had very rough periods with lots of cramping, so I had my first gyn visit at age 15 or 16. My mom got a referral from her ob/gyn for a teen friendly one. She was very nice and fairly young. She met with my mom and I together and then asked if she could meet with my separately.
I wasn't sexually active, nor would I be for a loooong time to come, so I didn't have anything to share, nor did I need to ask any questions.
I took birth control for a long time to control my periods and I know my dad picked them up for me....sometimes with me. You can imagine the looks he got from the pharmacy staff.
Be very open about what to expect. I have never loved going to the gyn...especially the exam part. I would get on line or get a book that talks about anatomy....a lot of women don't know their anatomy until after they are pregnant, and then even then some don't! :)
Make a fun day of it. Go to the appt and then have a girl's day out. This is a big deal and signals the end of childhood on some level. I would honor that and spend some time with her woman to woman.