Re: Understanding my mom's Tiaa-Cref account?
403B is just the non-profit version of the 401-K.
It does NOT have to be used as an annuity. Some of the TIAA fixed income options, however, can't be gotten out of quickly. I made the mistake of putting some of my money there and had to move it out of there over 10 years (still about three years to go to get all available to move). When you retire, you have the option of using the funds to buy several kinds of annuities. While the fees aren't as ridiculous as some other plans, it wouldn't be my choice. You can leave in TIAA-CREF and withdraw according to guidelines, or roll into an IRA, either self-directed or with an advisor.
I'm not currently aware of the their allocation options, since I left University teaching in 2001 and rolled all of my funds into a self-directed IRA. However, they certainly have the usual options available, from indexes, bond funds, money market funds, etc.
This then becomes a question of what you think the best allocation is, what you think the market will bring in the next X number of years, how much diversification you want, etc.
Other areas on this site have lots of ideas on that.