tummy time

My daughter hates tummy time. She's almost 12 weeks old and still won't hold her head up while doing tummy time. I just don't know what to do to help her, I know she can do it bc she hold her head up so well while I'm holding her. The doctor labeled her as mildly developmentally delayed. Any advice on helping her? I've tried toys, being propped, and me sitting at her level.