You won't ever be able to completely rescue it, but you might be able to make it useable (or, you know, giftable to any young girls you know!) by covering it in conditioner and gently pulling it lengthways and widthways to the knit stitches (not diagonally).
Yep..steep in hair conditioner or fabric conditioner to loosen the wool fibres. Leave it for about 30 mins. Then carefully squeeze the garment but dont wring it. Once you have squeezed most of the liquid out you roll in a towel to get the excess out. Place on a towel on a table and stretch carefully. Place paper weights on it to wear you want it stretched. It is very delicate at this point so be careful. Leave to dry like that. I havent done this but want to stretch a jumper and looked up you tube. Have a look on there.