Help! needs relationship advice?

i like this girl. she's the best friend of my sister. i always tell her that i like her but as a joke, so that i'll see what her reaction will be when i tell her the truth. she always responds like she only has platonic love for me but i'm not sure if she's joking or not since she always says it like a joke. one night we were both between tipsy and drunk and slept at the same bed. i kissed her and she kissed me back also. then i got to second base, but that's all we did.. what does this mean? does this mean that she also likes me? or just friends with benefits? i'm also afraid to admit it to her because she's always here at our house. i'm afraid that if i tell her and it may turn out bad, it will be awkward for the both of us the second thing is that i think she was just drunk, that's why she kissed me back...