If my letter 6475 only has my name on it. Should there be a separate letter for my wife if ewe always file jointly?

Yes she should get her own.  Is your letter for half?  Hers may come later.  Enter the total you got for both.  Check your bank account or Check your IRS account for each person 

Your Online Account | Internal Revenue Service

The IRS has been sending out letters to each spouse.   But even if you do not receive the letter, you must enter the correct total for the amount of the 3rd EIP you received.   If you are not sure then check your bank records from around mid-March onward for deposits of $1400 per person.   Or check the IRS account online:

https://www.irs.gov/payments/your-online-account

You want to enter the right amount or your refund will be delayed.   The IRS cross checks for mistakes and reduces your refund if you under-report the amount.