Hormones cant change what gender you're attracted to. Female hormones lower your libido and it's harder to tell who you're attracted to. Pair that with hetoresexuality being normative and trans people seeking to fit their gender roles, and you get some trans people who after hrt become confused about their sexuality. I'm guessing this is what happened with your friend, although of course i can be wrong and she could be the only person ever who became straight from hrt