Why does my freinds sister like to be naked? I also stole her thongs...?

I am 15 and she is 17 and she is smokin hot!!! My freind is super rich and his sis is hot. Whenever i go to his house, she is in her room naked. I went over to his house and spent the night and in the middle of the night, she came down with us to sleep with us because she was lonely. i took her thong off of her and stole it from her. she woke up naked. then the next day we went to the beach and she wore her bikini and a thong. about an hour into the day at the beach, she took off her top and went topless tanning, but didnt show anyhting. after that, she asked me (she was wearing a thong) to rub sun tan lotion on her. i rubbed it on her side and where thong was. on the way home, she was riding totally naked and i was sitting with her in the back in a three row seat with all seats occupied. she asked me to rub he s. the next time i went over to his house, i saw two aerie thongs and i took them along with a peek a boo bra. she is fine and i want to know if she likes me?