first when i looked at this i did not know they were separate pieces. I laughed wondering how does she get into this sweater. Silly me. However this seems pretty simple to make on the the bond so I am going to give it a go. Here are my Thoughts. cast on the length and knit the width. This could be another ttd creation! No fairisle though maybe later even cabled!
Approximately 32” around at lower edge x 19½” long
Whatever to get you this size just make sure you swatch.
Cast on 19 ½ “knit 32” sew side seam. This is knit straight without the ribbing on the top or bottom or without the fairisle.
You could knit 1” ribbing then you would knit 1 inch convert to 2 x1 rib knit 30 inch straight knit 1 convert to 2x1 rib.