As far as I know, if you are sent something in the post without actually having ordered it, the item is considered a gift and cannot be considered chargeable.
I remember at my old place of work they got sent a half dozen first aid kits they never ordered, from a company they'd never used or heard of and then 4 weeks later got an invoice for about £500.
Of course they refused to pay for something that wasn't asked for and got legal advice. The lawyers said to keep the items and quote this:
Under the Unsolicited Goods and Services Act 1971 (as amended), it is an offence to demand payment for goods known to be unsolicited and someone who receives goods in these circumstances may retain them as unconditional gift, and does not have to pay for or return any unwanted goods. If a consumer already has a relationship with the company, the terms of the agreement between the parties would need to be taken into account.
Taken from the
DTI, go to Question 13 near the end of the page.
You need to be sure she hasn't joined of those video clubs or something similar, but I'm sure if the above is quoted to them, they'll back off.