Estate Tax Portability

My wife and I have net worth of $15M.  If she dies before me, would her estate be able to transfer (portability) her Estate Tax Exemption amount to me?  Is all of the $15M community property? Would her Estate Tax only report her community number property half?  Is there any benefit to how the $15 M is registered?  (eg only $1M is registered in her name or jointly with me).