Bridesmaid Etiquette

Ok, here's the situation. My sister had asked me to be a bridesmaid in her wedding and had me buy a $175 dress to wear. Then she called off the wedding. Now the wedding is back on, but she is only having one bridesmaid and it's not me. So I asked what I'm supposed to do with this dress now and she said "Well (Bridesmaid) can wear it since she couldn't afford the dress last time." Umm... excuse me, I paid nearly 200 bucks for a dress so someone else can wear it? No. Then she said "wear it to the wedding anyway." Also a stupid idea. It is painfully obvious this is a bridesmaid dress. I'm not wearing a formal bridesmaid dress to a casual wedding when I'm not a bridesmaid. I would stand out like a sore thumb. Personally, I think she should reimburse me for the dress (at least 60-75% of the cost). But what is the right thing to do? Returning it is not an option. Resale shop would barely give me half I'm sure since its like 3 years out of style. Ugh. That's a lot of money to go to waste. EDIT: I believe she cut me out of the wedding just to be petty since I eloped and didn't have anyone at mine. Not like that's relevant, but that's the reason she left me out, there are already hard feelings.