To get to one hundred pounds? How tall are you? Not that it matters as just over 7 stone is not really a healthy weight unless your sub 5ft and built like a bird. Why are you so desperate to get to that weight?
Ure detremined and that can be a good thing. I advise u keep busy with leaning exercises and stick to fresh fruits and veggies. U can eat as many as u want, feel full and keep ur calories down. Although, remember ur body will need protin. Go lean, trukey, fish, ect.
Good luck with modeling. I hope it works out for you. But remember who u are and to love yourself. Ur dreams are important to follow.