Assalamu alaikum . Is vomit impure? If dress is stained with vomit should woman clean her dress?.

Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.

Yes, vomit is impure and would need to be washed off before prayer and the like. This should be done with water, and squeezing it out three times, or any other way of cleaning it thoroughly.

Allah Almighty knows best.