Fussy eater help

I have a fussy eater.. she is 2 year old and i have tried everything literally and she doesn’t eat anything she has started losing weight as well and worse thing is if she doesn’t eat for a long time and then eats something when really hungry she vomits it out!! Eh I don’t know what to do i cant give her junk whenever she is hungry because that’s what she only eats.. i think she has figured it out that we are bound to let her eat junk if she won’t eat anything else because hunger will make her sick