Wait, whoa! You now have an “inherited IRA”. Ask the “custodian” bank or mutual fund company how soon you MUST start withdrawals over your lifetime, and how much must be withdrawn each year. The balance should remain invested in the IRA, appropriately and perhaps more aggressively that your mother’s choices.
You definitely can’t add money to it. And you can’t convert it to a Roth. It should remain separate from your other investments and retirement plans, growing tax-deferred — subject to required annual withdrawals — as long as possible.