Thank you all. It's still a hard question for me to answer for myself, but your answers help.

I talked to L about it too today. We've talked about death before, but not in this way. I got 2 important messages from her. 1. Even though I can't really help my nieces at this stage, I do provide them with a role model who has good boundaries and loves them for who they are. 2. I do affect L. I do contribute to her life and I do bring her joy. That means a lot to me. She didn't try to guilt me into anything. I'm the one who asked those questions.