I don't think it is stealing as someone mentioned it is like picking something from a public bin. But I know how you feel, you should confront her, tell her if she wants anything you throw away she should ask you.
算偷野 coz' 樓主told 工人拿到屋苑的回收箱... she didn't listen to the order.. but worst of all, she took the stuffs for he r own.. that is 偷野...
If my boss told me to take the old computers to the charity centres.. instead of taking the computers to the centre, I took them home. I'm sure I was considered as stealing, too.
If I want the computers, I would have asked instead of just take them.