I think she should set up the Roth, to the extent possible within the earned income limitation. It's a simple matter of not generating potentially taxable income every single year.
I'm not sure if there is a tax-deferred account type she could set up and contribute "unearned" income. Any ideas?
If she has to go with a taxable account, look for a set-it-and-forget-it growth index fund or stocks that don't pay dividends. That way, its value can grow without flinging out potentially taxable earnings. If she needs cash flow, she can sell and incur taxes at the time of her choosing.
The only other trick I can think of would be to use the money as a down payment on a rental property. Then, use all your rent "profits" to improve - er... maintain - the property each year, so net income is near zero, even though your asset has appreciated. Finally, move into the property for a couple years, and then sell it for a tax-free profit. That's probably too complicated, LOL!