I often sent my kids outgrown clothes to an in-law, who was in a very hard situation financially, single parent with small children. Come to find out she was e-bay'ing many of the clothes, and her kids were going without. Mostly because "she didn't want to store them for a season." Pediapeds, name brand clothes, new clothes, etc.

I was personally offended - b/c I knew her kids
really needed clothes, and she'd only take a few items and sell the rest (and
not buy replacement clothes.) And then have the nerve to mention her kids' "needs" and her lack of funds to fulfill those needs. ugh.

: I don't send her anything anymore. Sad, but I can't in good heart send things for her children knowing she'll just sell them for cigarette money. Anyway... Now I donate, consign, or give to others.
That said, you have clothes you don't need and $ you do need. Consigning the clothes to buy what is needed is absolutely appropriate. Selling the clothes to but a DVD or pizza is different- if the giver was ever to learn of it.

Send auntie a thank-you, and if asked, be honest and say some did not fit/were wrong season and you're consigning or selling them for replacements. Just my 2 cents...