Performers are free to appear on the West Bank and Missy could certainly appear if invited. Boney M has just appeared at a Festival (after promising not to sing "By the Banks of Babylon" which apparently refers to Israel! Btw, Leonard Cohen wanted to appear in Palestine but for reasons that no one understood, they decided that they didn't want him after he appeared in Israel! The business with Chomsky was simply a stupid mistake on behalf of some official. The man is virulently anti-Israel but he should have been allowed in without any problems.
Three killed after car bomb explodes in Sana'a, Yemen (Reuters)
from the article: Jethro Tull: Won't be pressured into canceling planned Israel show