I LIKE THIS GIRL BUT SHE DOESENT EVEN NOTICE ME WHAT SHOULD I DO!?

THERE IS THIS GIRL IN MY SCHOOL AND I LIKE HER BUT MY SISTER HANGS OUT WITH HER MOST OF THE TIME BUT SHE DOESENT EVEN KNOW WHO I AM IDK WHAT I SHOULD DO I AM KINDA SHY AND CANT TALK TO HER IDK WHY ANYWAYS TODAY HER AND HER FRIENDS KEPT ON LOOKING AT ME TODAY CAUSE ONE OF HER FRIENDS I AM RELLY GOOD FRIENDS WITH. SO SHE SAYS HI AND WHEN I LOOKED ALL OF THEM SAW ME IDK IF I SHLD SAY HI I WUZ TXING HER THE OTHER DAY BUT SHE STOPED TEXING ME I THINK CAUSE MY SIS TOLD HER TO STOP I ASKED HER IF SHE WUZ MAD AT ME SHE SAID NO THEN SHE STOPED AGAIN I DONT WANT TO TEX HER AGAIN CAUSE I DONT WANT TO SOUND SO PUSHY AND BE ANNOYING HER I WANT TO ASK HER BUT 1 THING IM KINDA SHY!!! I NEED HELP!