How to meet my mother?

Im a 22 year old woman and i was disowned by my parents for being lesbian, but ive recently found out that the woman who raised and disowned me wasnt my real mother apparently my dad divorced her and banned her from seeing me, my grandma has told me that my real mother has asked her about me, i would like to meet her and my grandma has given me her address, i dont know how though, should i take my wonderful girlfriend of 3 years Sara, should i dress up and wear a nice dress, im very feminine, i dont know what she knows, i dont know what my grandma has told her, dont know if my mother knows that im a lesbian