It depends on why ballerina gave her SIL the clothes, in the first place.
If it was to help her SIL out, then she did. Her SIL was able to sell the items, and put the money towards the cost of replacing them.
If it was to reduce environmental impact of her SIL buying new items, again, this was a success. Although the SIL bought new items, the person that bought the old ones did not, so fewer new goods had to be produced.
If ballerina gave them away as an easy solution to a load of clutter she thought she had no further use for, again, a success.
If it was to make her feel a bit superior to SIL, that she had been able to buy new items, but her SIL had not, well this was a partial fail, because the SIL did buy new items, but only with ballerina's assistance. So, she still does get to feel a bit superior.
I do think it was a little impolite of the SIL to sell the items, without checking with ballerina first. If ballerina had known her SIL would sell them, she may not have given them. But I also think that if ballerina's sentiments were purely altruistic, she wouldn't mind what had happened to the items, once they had been given away. They were, after all, a gift.