Thanks for all the suggestions.
The goal is for the long haul, retirement.
We have educated her on the principles of investing so she can have a grasp on how it all works and especially how compounding interest works over time.
Now being 17, like most teens, the concept of retirement is quite abstract. But it is interesting to see her face glow when plugging a few numbers into a retirement calculator and seeing how starting as early as possible has a profound effect on future funds.
Well then! Analytically speaking the IRA is her choice, and presuming her income is low (part time, 17yo) she'd be well served with a Roth IRA.
As for education, the most notable lesson which stuck with me as a teenager was when my dad showed me "the graph" of how compounding at different ages worked. I had older siblings and I remember him showing me how if we all started saving today I'd almost certainly become a millionaire but they would need to save a lot more if they ever hoped to do the same. He also introduced me to the concept of 'FU' money (but didn't use that exact phrase) - telling me if I socked away money in my teens it would give me enormous flexibility in choosing only the jobs I wanted in my 30s - and he was right!
Anyway, I applaud you and your step-daughter for getting an early edge in financial security. If more people took this approach a lot of our societal problems would melt away...
