Potential Will Contest: My Mother dies and is named in her Stepmothers Will

My Mother just passed away in Chicago, her Father died in 1991 leaving his estate to his second wife, she suffers from some dementia and is in a nursing facility in Florida.

My Mother left her estate to her 4 daughters, My Mother is named in her Stepmothers Will. We were told by our Step Grandmother she would have to change her will and we cannot be named because we are not family. Yet, our Grandfather was my Moms father.

Do we have a basis to actually contest this after she dies?