Athletic shoes, barely worn

I bought these online, not realizing they didn't have a central post, so they don't fit well. Plus, I let my mom try them for a day and she got a stain on them (how though, I don't know. She can get stains on anything). I have tried to get the stain out but to no avail. Then, I lost 80 lbs and did you know losing that much weight can make your feet shrink? Yeah, neither did I. These are huge on me.