TIAA-CREF is a custodian offering conventional investment options only. You can't use that to invest in alternative assets such as real estate. She needs to rollover her account to self-directed IRA with a custodian allowing alternative investments and then she would be able to invest her IRA funds into real estate.
As has been noted, TIAA-Cref does not facilitate investments into non-traditional assets. The services of a specialty provider are required.
I wanted to add that if your wife is still employed with the college and is under age 59 1/2, she probably does not have the option to rollover any of her current plan to another plan of her choosing.
Have her check with her plan administrator to determine if and what amount of her current play may be eligible to rollover to an IRA before you spend any additional time on this topic.
Thanks everyone for confirming this topic! Your time for responding is greatly appreciated!