On the face of it, struggling to see the problem (based on the account as presented). If the problem was that they were the wrong size, surely store credit would enable them to be replaced with the correct size?
As far as contract law is concerned, an item is only sold for a specific purpose if that purpose is either self-evident or communicated to the seller before the transaction - so from a legal perspective, whilst it might have been bought as a gift, it was not sold as one (to the extent that that is relevant). As regards it being ridiculous that a cash refund is not available for items purchased in-store where to all intents and purposes the purchaser simply changed their mind, this forum is for legal advice, not for entertaining deluded rants from those who feel hard-done-by from the fact that the law does not give them unilateral rights to unwind a contract of sale.
