Comorbid conditions - struggling with sisters depression

Hi everyone! This is my first post here; but long story short - I'm really struggling with my sisters depression. She is my younger sister, and we have an immensely close bond. However, I have ADHD and mild OCD (making me very intense, emotional and high energy) and during COVID-19 I have also really struggled with anxiety (particularly to do with me worrying about her). My younger sister has had depression for 4 years now, and whilst she (to many) appears to be doing a lot better, I am anxious every day that she is going to do something to harm herself. I'm unsure if this fear is stemming from my own anxieties and obsessive tendencies (particularly because there's been 'suicide clusters' in the area I'm from and it's all over the media so I can't stop thinking about it); and I'm having a hard time working out the right way to give her care and love, but also not smother her when she's having 'off' days. I am nervous that my constant panic, checking in on her and emotional state will make her feel smotherered and drained... long story short, I'm struggling to trust that when she says she's fine, that she will actually be okay. Does anyone else struggle with this, when living with someone with mental illness? That constant fear and worry no matter how much reassurance you get from the person. Any advice / personal experiences would be super appreciative.

Thanks 🙂