Hi Lilly:
My great grandmother was born in the 1800's in Guayama, Puerto Rico. Her name was Herminia Yejo. She had a sister and a few brothers. Her other sister was named Rafaela Yejo. I am not sure if your great grandmother was Rafaela. It cannot be Herminia because she only had one daughter Mercedez (my grandmother. She died giving birth. The other way to trace them is to join groups like searching for your roots,
http://www.pr-roots.com/index.htm. You might find somethings here, but they do not have birth certificates for people born in PR prior to 1900's. You might have better luck using a local ancestry group that can direct you properly.