Even if you are above the Roth income limits, you can do a Roth IRA by contributing to a non-deductible IRA and then converting to a "backdoor" Roth. There is no income limit for conversions. However, if you have both deductible and non-deductible contributions to a traditional IRA, you have to convert pro-rata. You can't just convert the post-tax portion
https://support.taxslayer.com/hc/en-us/articles/14776395451021-Pro-Rata-rules-for-Roth-conversions-Backdoor-Roth-
The rules for an inherited Roth IRA changed recently but in most cases you'd roll it over to an inherited IRA account and end up having to withdraw in 10 years. Here's the IRS discussion on that:
https://www.irs.gov/retirement-plans/plan-participant-employee/retirement-topics-beneficiary
If the account is at least 5 years old at the time of any withdrawal (including time your Mom held the account) , withdrawals from a Roth, including earnings, are tax free.