When a Sibling Drifts from Faith

Salam everyone, I just need to let this out and maybe get some advice. I’m 16 and my older sister is 19. Over the past year, I’ve watched her slowly pull away from Islam. She used to be a typical Muslim, but then she started dealing with really bad mental health-like, she’d obsess over tiny, tiny things and it would just eat her up with guilt. I’m talking about stuff most people wouldn’t even notice, but to her, it was this huge weight. We’d talk about what was bothering her, and it was always these little things, but she’d overthink them until she thought she was a terrible person. I kept telling her to try therapy. Then around March, she had this complete breakdown-started blaming Allah, asking why He would put her through this. It scared me, honestly. She got past that episode, alhamdulillah, and people comforted her, but I still kept suggesting therapy. Now, she wears hijab and goes to Islamic events, but I suspect it’s just to keep up appearances for our parents-we come from a very practicing household. I don’t think she prays, and I’ve seen her eat non-halal food. I’m at a loss. How do I even talk to her about this? I’m worried, but I don’t want to push her away. Any advice, especially from an Islamic perspective, is welcome.