This is a classic, elegantly white look with a little bit of an edge because of those shoes. Those are shoes that you need to kick your enemies with. It looks like this is on the Jimmy Fallon Show, so if he beats her in one of his little games, she could always give him a bloody kick to the shin.
Stranger Things Fact Number Twenty: At the end of Season One, Eleven has to float in an epsom salt bath using 1,200 pounds of salt. The thing is, they actually had to use 1,200 pounds of salt. You can't CGI that kind of thing. That means she really floated in all that salt. That's how you make a well-seasoned actress, if you know what I mean. I swear. These jokes just come to me.