dilemma

Sorry for the long post(This is my first tike posting on this so please excuse if i dont know how thus works). Ok , so me and my gf of 5 years have broken up recently due to her being very aggressive and abusive .Her step-sister comes over for the weekend to come visit and hears the news about us . she talks to me and tells me that she has grown fond of me and actually likes me. I didnt know how to react and i told her that i found her attractive and sometikes i would think what would happen what if me and her were to date. Her father really likes me and still wants me to be a part of his family , even though i broke up with my gf ( his step-daughter) and im in a situation where she kissed me and she doesnt know how if she wants to risk us being together. I told her i would wait and play my cards here while shes back at home, yet she tells me that she needs time to think about it . i guess what im asking is.... Is this wrong ? Should i wait for her to make a decision? Is it worth taking the risk ? ( im also trying tell her father[biological]about our situation but im just to nervous), (my ex-gf step father ). I really would like to see how the future with me and this girl would play out , but should i feel guilty? Tl:DR , me and gf broke up, step-sister comes over and finds out we broke up . she tells me her feeling about me and we kissed/made-out . she wants this to be a thing but shes scared of what everyone will think about her. What do i do?