BIOLOGICAL FACT THAT HORMONES REGULATE BIOLOGICAL FUNCTION.
SOME biological functions.
Her bone density WILL increase, her muscle mass WILL increase
SOME. But especially when started after puberty, these changes are relatively small and will never equal that of an average biological male. And the reverse (moving male to female) is even more true. Muscle mass and bone density changes are small when hormone therapy begins post puberty.
her hip shape WILL change because HORMONES REGULATE BIOLOGICAL PROCESSES.
False. Skeletal structure is set during puberty. In particular, the pelvis shape is set in stone. You can give the person lethal doses of testosterone and not alter the pelvis to look like that of a male. You don't know what you're talking about.
any benefit you might have gained being born with a penis or a vagina is basically nullified after a relatively short period of time.
100% false. Hormones regulate a subset of biological processes. If I give you the hormones of a bird, you will not take flight. You can make more significant changes if you're giving hormones to per-pubescent children, but that idea is highly controversial. Post-puberty, you can cause some level of soft tissue changes with hormones. You cannot change brain structure or skeletal structure. It just isn't a thing that's real.
And none of that is to say that a person who transitions doesn't deserve love, respect, support, safety, etc. They absolutely do. They deserve basic human dignity and compassion. But love, respect, and compassion do not include forcing others to accept bullshit claims about biology. It is Orwellian to attempt to force it.
There. Are. Four. Lights.