Is a Traditional or Roth IRA a better option for someone who's never had a full-time job?
You don't mention whether she is now working or where the $6500 would come from. If she has no earned income she can't contribute to any type of IRA. However, if she inherited a Traditional spousal IRA she may want to do annual Roth conversions up to the standard deduction & exemption limit of $10,400 (2017) (You'll need advice from whoever does her taxes to determine the maximum amount she can convert each year.) A substantial IRA could cause her to have taxable income at age 70.5 so it would be sweet to make it all tax free before then. If she inherited the IRA from a parent, then Roth conversions aren't available.
If she is recently widowed, like in the last year, you may need to give her more time to grieve before making major decisions. Cash is king in these types of life changing events. She has to have earned income to be able to contribute to IRA's, Roth or Traditional. If she has earned income, I'd seriously look at Roth IRA's. There are other factors to consider such as current and future sources of income, current debt, are there major expenses in the near future, make sure she has 6-9 months in an emergency fund at her local bank (somewhere it's easily accessible and very liquid).
Does she work now? She needs to have earned income in order to contribute to an IRA. If so, either Roth or Traditional would be fine. The money would need to stay in the Roth for five years (age 61) in order to receive the growth tax-free. If withdrawn sooner, the earnings would be taxed. The principal investment into the Roth IRA would however be returned tax-free. She will need to file IRS Form 8606 with her tax-return, otherwise the entire Roth amount will end up getting taxed and penalized 10%. She can withdraw all her money from IRA's and still contribute again as long as she has earned income.
The IRS limits contributions to IRAs to the lesser of $6,500 (for those over age 50) or "taxable compensation". This likely means your mother is not eligible to contribute to an IRA, unless she has begun earning a salary or self employment income. Beyond that consideration, the general benefit of an IRA in the first place is income tax deferral, and per your description her tax liability seems to be minimal.
For reference, the IRS website has a fairly straightforward explanation of contribution limits on this page: