If you are on a fixed term AST (assured shorthold tenancy) e.g. a 6 month tenancy, you cannot be evicted until the end of the fixed term. Even then you probably wouldn't be physically evicted for several months while it went through the Courts and bailiffs were arranged. Also, she would need to issue you with a correctly filled out s21 form giving you notice that your tenancy will be terminated. The s21 can be served anytime during the tenancy but can't take effect until the end of the fixed term. Without the s21 you can't be evicted unless you owe 2 or more month's rent.
So, no, she can't just evict you on a whim but has to follow the legal procedure (and it's quite easy to get the procedure wrong).