Am I a shitty sister?

I’ve tried and tried and tried over and over again to help my sister. I’ve lended her money, i have given her the benefit of the doubt, but I just feel like there is no helping her anymore. Itsbeen about 7 years and I have given up on her. I’ve given up on trying to help her get out of the relationship, and situation she is in. There’s no helping someone unless they want to be helped and I feel awful saying this out loud but I’m drained and I’m giving up on her. I’m her family, and I will never be able to 100% give up on her. She’s my sister and I love her, but what are you supposed to do? When is enough enough? I hope she finds a way out of her relationship and gets the help she and her kids need. I pray that her toxic relationship doesn’t take her from me, but the truth of it all is that she’s not going to leave until she is ready. All I feel like I can do at this point, is pray. Has anyone gone through this before? I love my niece and nephew, but their parents have done nothing but push family away. I feel bad for the kids...