my girlfriend has recently come out to me as transgender (ftm) but she's too young to transition (only 15 years old) and she doesn't know if she can be bothered with the whole T process, ontop of this, her family is very unsupportive of trans people. they're okay with gays and lesbians but transgenders are too far.

i'm female and i'm bisexual so it wouldn't seem like this should bother me, and it doesn't, i'm just struggling. i swing more towards girls and are very physically and emotionally attracted to them (i mean, vaginas, come on) but i don't feel the same way towards boys and don't think i could ever sleep with one?? i just think they're hot and have a romantic and emotional attraction to the male gender.

i have know my girlfriend for five years now and we have been together for about 6 months. about a year ago, she was admitted to a hospital for anorexia as she was 40lbs at age 14 at a height of 5'7. obviously, because of this, her body changed shape and she lost her curves and her boobs disappeared and i guess she loved this body shape because she now wants a masculine figure like she once had. she's still recovering from her anorexia but this is different. 

she purchased a dildo a couple months ago and everytime we've used it (sorry if this is too much information), she doesn't want to take it off after, and sometimes she tends to just put it on once she's woken up (it's a strapless strap-on) and will wear it for the majority of the day. recently she's been searching for prosphetics and is hoping to order one soon.

she's always checking with me to see if this is all making me uncomfortable and i always tell her it isn't, because it's not, and i'll tell her i'm not going to leave, because i definitely don't want to.

i'm just scared that once she starts T and gets a prosphetic, i would start feeling different and i wouldn't be as attracted to her and i know that i would miss the old immy, even though she wouldn't be gone, i'd miss her boobs and her vagina and her voice and her face and just, everything. i know it sounds really selfish but i'm struggling hard and i don't know how to talk to her about it because i don't want her to hate herself even more and i really really don't want to leave her because she's everything to me but i know that if i stay with her and start to lose feelings then i know that someone will get seriously hurt. 

i just need some advice, please, anyone?