Crazy halloween night

So every year i host a halloween party at my house. My family and friends come over. My parents adopted a gitl when she was 5 i was 13. Now shes 18 she came over with my mom we were all drinking having a great time. At the end of the night everyone left except my mom and sister. Well my mom is asleep in the guest room, my girlfriend is asleep in the bedroom and me and my sister are down in my mancave watching movies. She tells me to close my eyes she has a surprise for me, so i fo it. Next thing i know she kisses me and sits on my lap. I open ny eyes and realize shes taken off her costume and she's just in her bra and a thong. I lost control and we had sex all night long till i left to go shower and sleep. Next morning everything is normal. I think she may not remember, we both were drunk but i don't know what to do next.