Why did she say that about me?

so me and this girl where talkin but we only talked like 4 or 5 times cus we didnt see each other that much...but recently she told my sister that she thought i was lame and that i try to much to talk to her,and that shocked me cus really we didnt know each other that much and we really talk that much, i mean i remember one time we talked and she missed her bus to go home because she was talkin to me and the only reason she noticed was because i told her she was gona miss it,i mean that made me think twice,if i was really lame wouldnt be obvious to use the bus as excuse to stop talkin to me...i remember at first when we seen each other she kept starin n stuff so i decided to talk to her and i mean wen we barely met each other she would laugh at things that i said that were cheesy,but wat i think she started to act different and stuff was because she told my sister i was cute and my sister told her eeww thats my brother and she stayed quiet and all she said was dont worry bout it hes not my type,i think i would of a chance with her if it wasnt cus of my sister,i mean there like best friends....bt yea umm what i wana know is why she said that?