As I mentioned previously, I've never run into this situation in my practice.  With that said, I did a little research and came across this article.  Based solely on what I read, it looks like the roll-over into her own Roth IRA may be an option.  Since I don't know all the specifics, I can't comment for sure though.  Good luck. 

What Is the Roth IRA 5-Year Rule? When It Applies, Whom It Affects (businessinsider.com)

The 5-year rule for inherited Roth IRAs

The final 5-year rule applies to inherited Roth IRAs. Roth IRA beneficiaries can withdraw contributions from an inherited Roth account at any time (in fact, they're required to). But to withdraw earnings tax-free, the account must have been open for at least five years when the original account-holder died.

If the account hasn't been open that long, there are a few options:

• Disclaim the inherited assets. You can choose not to accept the funds if you don't need the money or don't want to deal with the tax consequences.
• Withdraw the money in a lump sum. You'll have to pay taxes on the earnings portion of the account all at once, but this might be better if you're in a low bracket now.
• Withdraw funds annually based on your life expectancy. This option is only available to surviving spouses, minor children of the account holder, disabled or chronically ill people, and beneficiaries who are less than 10 years younger than the deceased (for example, a sibling). The beneficiary's life expectancy is based on the IRS Single Life Expectancy Table.
• Roll the inherited funds into your own Roth IRA or a new Roth IRA account. This option is only available to surviving spouses.
• Delay withdrawals. You can leave the money in the account until the 5-year mark has passed. The Setting Every Community Up for Retirement Enhancement (SECURE) Act mandates that, for most beneficiaries, inherited IRAs must be emptied within a decade. The beneficiary owes a 50% penalty on any assets left in the account at the end of the 10th year.