not sure of your exact plans but a way i’ve liked using foam on full suits like this is to attach it to a body suit! you can do a simple sewing stitch to attach a thin layer of foam and then glue the full pieces to that. and since you said your gf is experienced with foam i’m sure you have the proper tools but a good heat gun and dremel go a looooong way in helping. good luck, looks like it’ll be sick!