People over age 72 (70.5 until a couple of years ago) are required to take a distribution, from their IRA (except a Roth IRA) of a certain amount each year ( the RMD -Required Minimum Distribution). So your mother was required to take money out of her IRA, regardless of what she did with it*. At age 90, she was required to withdraw 8.2% of the money in her account at the beginning if the year.
*The only way to avoid tax on the distribution is with a Qualified Charitable Distribution (QCD)
