Elegant Sleeveless Long Mermaid Prom Dress With Slit

I open the package that I’ve waited 27 or so days for- so excited for this dress!! It was a risk to take since it didn’t show a picture of the back of the dress but I fell in love with it- but anyways I open this package, pull out the dress, put it on along with my shoes and what does my mother point out? Some black stuff on it nobody knows how to get off. The material is soft and the sparkles are just falling off-
The slit is so high you can’t even wear underwear with it- I can stitch that to my liking tho. It’s a very pretty dress but the fact it came with a stain?? What. The. Hell.
I’m taking it to a dry cleaner to try and get it out soon.
I added a picture of the back as well as the stain I’m talking about. It doesn’t show up the way I’d hope on camera.

I've been wanting to post this all week.