Missing teen girl in blue hoodie

I lost my sister yesterday around 3pm near the Great Falls Library on 7th Street. She's about 5 ft 4 in with shoulder-length black hair in a ponytail, wearing a bright blue hoodie, black leggings, and white sneakers. She has a small crescent tattoo on her left wrist and a turquoise bracelet with a silver compass charm. Last seen heading toward the Riverwalk, possibly toward Central Avenue near the skate park by the Civic Center. I'm really worried—she's 15 and doesn't have her phone. If you saw her or know anything, please contact me.