I always made my queen size quilts close to the batting size of 90" wide by 108" length. The pattern and border widths can control somewhat the final size you make. You might go over the measurement with her with someone's queen size bed to show her the dimensions. The last Queen I made for a friend, she wanted the sides to hang over more like a bedspread and I ended up piecing an almost king size quilt. Fortunately, I gave her the top of the quilt done in her favorite fabric and she had it quilted.