Sometimes people are rude and insulting but you don't have to take it personally or necessarily confront it, even if you don't feel good about it.

You already said your sister-in-law is a snob. So, who cares what she thinks? The most important relationship in that picture is between you and your husband, and it didn't sound like you had any problems with him or vice versa.

Bottom line is that other people have problems too and sometimes it is best to let things slide. After all, we all want other people to overlook our own behavior problems! If this is not just a one-time type of thing but is recurrent, that is a different situation and you have to assess whether it is better to find a way to talk to her about it, or to just avoid/minimize situations where you have to deal with her.

Good luck!