I don't that she is doing something wrong.
When you give something to another person, that item becomes theirs to do with as they like. If you don't like the way they decide to use it, too bad. It's theirs, not yours. Don't give stuff to them next time if it bothers you. You don't get to dictate how people use their own things, no matter where they got them from. And a gift with strings attached isn't really a gift. As soon as it becomes theirs, it's theirs. They can re-gift, disassemble, paint it, smash it, or whatever they like. It belongs to them and people can do what they like with their own belongings. It is not automatically rude to use your own items as your own.
Selling things on Facebook always strikes me as a little tacky, but that's about it. We can all easily understand wanting to get rid of things which are linked emotionally to a part of your life you want to move on from. And for all we know, she suddenly is having trouble financially or something. Who knows.
The point is, the item is hers, and she can do whatever she likes with it. There isn't anything wrong with that.