As you say now't so queer as folks ......had a 'friend' who would call me any time of day or night as she had an urgent need to talk ! Call me early morning saying she just MUST see me ...so off I would go, neglecting all else, to rush to be with her to hear her going on and on and one about her soon to be ex husband (and she was by then 70 so not a young chic !) ...I would buy her coffee then hope to get home to lunch but no she wanted to have lunch as well ,,,,this went on for four years ,,,including the time she had an accident on holiday and asked me to go to her insurance co to sort out paying the clinic in Cyprus and organising her re patriation ! Shortly after she got back she said she was moving house and would I help her pack and get some things sold on E bay > Yes of course I said ,,,,,then one day some weeks later I went past her house on my way to my hairdresser and there was a removal van and other friends packing things into it ,,,I called down the hallway ...oh I didn't hear from you but if I can help, you know where I am ! No call, no thanks, no goodbye ! Later learned she had moved again, back to the UK ....a month ago I was having coffee in a local café when she walked in with two other friends ,,,,I said Hi ! lovely to see you ...reaction : Do I know you ?' .....couldn't believe it ! no explanation, she doesn't have any mental or physical illness ,,,all very odd ! but you must let it go and get on with life ! These things happen ...oh and if I ever received a pressie that was the wrong size I would recycle it to someone it would fit ,,,and if I gave any clothing as a gift I always sent the receipt In a separate envelope so the person could take it back for a refund or an exchange ,,,,what else they did with it was up to them ! oh and I would never have returned anything to the giver ,,,,that was the big mistake I think !
Move on, be glad you had a good friend for so many years and maybe put your efforts into helping a charity shop or some such which will help others and give you enormous satisfaction ! Good luck !