Kindly refer to the following link(s):
Is it permissible for women to wear a ring on the index finger? (website)
Is it prohibited to wear rings in the index and middle finger for both men and women?
Ruling on wearing rings on the index and middle finger for both men and women
It is an issue of dispute. There is a hadeeth in Saheeh Muslim where the Prophet salla Allahu alaihi wa sallam forbade from wearing the RING on the middle or the index finger. Some scholars say that this is only for males. I believe that it is general and for all genders.