Well, she isn't a guy and never will be, so there's that. You might suggest to her that she reads some detrans stories either here or on reddit, because even if she does wind up passing as a guy at some point there are likely aspects of it that she hasn't thought about. Most tif's don't get a sexual thrill from larping as a dude, and many find that the reality of it is much more difficult than they anticipated, so the end results is less rewarding for many. You know how most women will smile back at you if you smile at them? Well, if you're a man and you smile at a random woman odds are she's going to think you're a creep. And there's a hundred other small nuances that she likely hasn't considered. Not to mention the damage T does to your body, heart problems, middle aged acne and who knows what else. Oh, and what's her sexuality? Because a good many straight women aren't interested in a guy who has a vag and not a dick, and certainly not many lesbians are turned on by a woman with a beard.