can she prove that she has enough money to pay for your fee? if yes, how then? you will need to prove that through taxes paid, etc.
sister sponsoring is actually not gonna work so much in your favor. u dont have ur own funds and sister is PR + ur sponsor, u will look like a prospective immigrant,which is not what u want.
so try showing own funds. if u can't go ahead, write a good SOP. it's still very possible to get visa.