Asalaam
first of all Ameen to all dua, secondly don't worry inshallah Almighty Allah will do best with you, keep faith in him.
best of luck in this hard time.
never loose hope, you never know in What Almighty allah has chosen best for you.
sorry but this is about more than just fasting..your fiance has already told you she doesnt believe in islam..seems you have converted and just assumed that your finacee will share your love of islam..she tried fasting because she loves you..but she has told you she doesnt believe in islam..what more do you want her to say..you made your choice ..now she must make hers..