Are you planning on rolling like accounts together, so that you will end up with only three accounts: your Roth, your tIRA, her Roth?
You could move your accounts first, use yourself as the guinea pig, and then show her the results. Selling points: lower fees, simplifying number of accounts (if you are doing this), having all accounts at one consistent place and visible together. It is nice having DH's Roth IRA and rollover IRAs show up on one screen, rather than in two different places.
I don't understand the comment about being comfortable with mutual funds. You can use MF at Vanguard. Maybe DW needs to see what Vanguard offers?