The Turbotax website does not allow me choose standard or to itemize? My spouse had not even filed her taxes yet.

TurboTax will compute which is best- in other words once you have entered enough itemized deductions to exceed the standard, it will switch to itemized. 

However you can change it.  According to How do I change from the standard deduction to itemized (or vice-versa), here is how to change from the standard deduction to itemized deductions:

1. "Go to the screen: Based on what you told us, [either Standard Deduction or Itemizing deductions] is right for you, and select Change my deduction.
2. On the Which deduction do you want to take this year? popup, you'll see the dollar value of each deduction type.
3. Select the type of deduction you want and select Continue twice."

In lieu of using the link in step 1, you can also navigate to Federal > Deductions & Credits and then continue through all the interview pages, and at the end you will arrive at the same screen, where it says which is right for you and there is an option to change it.

And  May I ask why you want to file Married filing Separate?  When you start the return and say you are Married and not  filing together you need to enter her name and then check...Either her or I claim itemized deductions.  

Unless you have a specific reason to file separate returns,

It is usually better to file Joint. Joint has the lowest tax rates and the highest Standard Deduction. And if you are in a Community Property state MFS gets tricky to figure out. See,
https://ttlc.intuit.com/community/married/help/married-filing-separately-in-community-property-states/01/26030

And How should you file…..
https://turbotax.intuit.com/tax-tips/marriage/should-you-and-your-spouse-file-taxes-jointly-or-separately/L7gyjnqyM?srsltid=AfmBOopGqCNexowW0pYgvsf7ycIkrx4VjO_63UXv6vSnfu3UEGQiKQTh

Here's some things to consider about filing separately……

In the first place you each have to file a separate return, so that's two returns. And if you are using the Online version that means using 2 accounts and paying the fees twice.

Many people think they come out better when filing Married Filing Separate but they are probably doing it wrong. If one person itemizes deductions then the other one must itemize too, even if it's less than the standard deduction, even if it is ZERO!

And there are several credits you can't take when filing separately, like the

EITC Earned Income Tax Credit

Child Care Credit

Educational Deductions and Credits

And contributions to IRA and ROTH IRA are limited when you file MFS.

Also if you file Married Filing Separately up to 85`% of your Social Security becomes taxable right away even with zero other income.

See …….
https://ttlc.intuit.com/community/married/help/is-it-better-for-a-married-couple-to-file-jointly-or-separately/00/25590