My sister refuses help

My 19 yo sister has been dealing with a lot lately and some very obvious depression symptoms started showing on her, I tried to talk to her, support her, shower her with love and gifts and I offered her to see a therapist and I’d love to pay for it. She refuses the whole thing
She’s like a daughter to me. Like, I raised her, I protected her with all my soul in our toxic household and I can’t bear seeing her like this, my heart aches for her. She’s all I got and idk what should I do at this point fr