I don't know the answer to this (I live in Illinois) but this is a resource shared on another local Chicago message board - https://thelilactree.org/

It's a non-profit that provides info and resources for women wanting divorce. That's a good place to start.

My SIL (DH’s sister) is headed for divorce. I recommended that she discuss a legal separation agreement with an IL attorney. She spoke to an attorney she knows who supposedly handles family law matters, and was told that legal separation is not a thing in IL.

My brief Google search does not support that. I found some legal aid resources for her, IL bar attorney search, and some law firms that provide free or affordable initial consults.

Does anyone have any idea why a family law atty would tell my SIL that legal separation is not a thing in IL? Thank you.