I beat the game on normal and started a new game on veteran with Chris but I want to play it as Sheave is there a way to start a new game? All I get when I start up the game is to continue from where I last started (Ch 1-1)

Can't you just press New Game +?

New Game + is now 'Continue'

• Chapter Select
• Pick a Chapter
• Select "Sheva" as Your Character
• Success!
  

Just select the very first level on chapter selection screen. It's equivalent to starting a new game.

If you really insist that you want to hit "new game+"  to start a new game, just use chapter selection to choose and beat the last level again, and your "continue" will then be replaced with "new game+."

As for playing as Sheva, you should be able to select her as your charater every time you choose a chapter in chapter selection screen or every time you select new game+.