Does these girl like me? Should i approach her?

I am 17 years. There is these beautiful girl I have been eyeing for four months now and badly need her. She is a reserved type and she is always at home with her mother. She is definitely single. Sometimes she walks with her friend and she is extremely cute. She likes looking at me when I am out of peripherals. She probably knows I like her. I tried to avoid looking at her for some time and then one day I was doing shopping and she walked by and smiled at me. God that was sweet. Her friend tries to speak with me often but I have never told her about her friend. I am just confused as whether to approach her or tell her friend about it. I nee help. Both girls and boys are invited into these.