A backdoor Roth is only necessary if she exceeds the income limits for a regular Roth. For 2019, the contribution starts to phase out for singles at an MAGI of $122k and fully phases out at $137k.
If her MAGI exceeds $122k, then she can open a traditional IRA, fund it, and then roll that money over to an existing Roth before it earns any gains. I did this last year, and it's just as stupid easy as it sounds. The tax reporting isn't so straight-forward, but I even managed to figure that out. If done correctly, backdoor Roth contributions do not affect your taxes because that money has already been taxed.
The max contribution to a Roth for 2019 is $6k. If she did not put any money in an IRA last year, she can contribute to the Roth for 2018 and 2019, if she does so by April 15.
The rest of the money, I'd put in a "high interest" money market or CD with someone like Capital One. Their money market account is 2%, and a one year CD was at 2.7%, last I checked.