About marrying someone’s daughter whom I call as sister

Assalamualaikum, The question I have is about a marriage proposal, where the girl is my relative abd I call her “sister”. In which way she is my sister is “she is my mom’s father’s younger brother’s daughter’s daughter” I hope you understand the family tree. So coming to the point can I marry her. I need some clear answers, so that I can make my decisions further. Assalamualaikumasalam.