In all likelihood, yes, she will lose.
But she should still run for the same reasons Bernie ran. Change the discourse and prevent unfettered ratcheting of the Overton window; force Democrats to respond to her challenge.
If she doesn't run, we all lose. Winning isn't quite everything.
I have a significant colony of false widows (steatoda) around the house. They're very chill and mostly stay outside and make webs in corners.