My sister is a ped, and she routinely does pelvics on sexually active teens in her office. Why in the world would your DSD's mom want to take her to a GYN when her ped can answer any and all questions, and do all the necessary sex education and tests, incl. the HPV vax? That's what I'm not getting. A ped would be much less likely to do a pelvic or any other testing or whatever than a gyn, simply because the gyn would be automatically thinking along those lines, whereas her ped already has an established relationship and knows DSD's health issues.
That is, assuming she has a ped. If not, ignore me.
As for the rectal, never had it. Ack.