I have sometimes had buyers purchase from me on two of my ids at the same time, obviously I can't combine them so I tell them I will cancel the bids on the second id and add the cost to the postage of the other items, has always worked up to now. You could do much the same, just tell her to buy 3 and you will end the other one and add it in as postage. Ebay are still getting their fees and the buyer still has their buyer protection.