Do not take a ticket that has a stop or connection in Africa. Be especially careful about "direct" flights as these do stop and can often require passengers to change to another aircraft even though the same flight number is used. To reiterate: direct flights are NOT nonstop and should also be avoided.

Given that your location is DTW, the obvious choices would be DL through ATL or JFK--I'm not sure how their schedule to JNB looks--or DL connections through AMS or CDG, ideally nonstop from DTW to Europe, although connecting at MSP to the MSP-AMS or MSP-CDG TATL nonstops is easy. (For an inexperienced young traveler, I would avoid JFK and probably also ATL as overwhelming; MEM or CVG or even PIT would be easy but these sub hubs tend to fly 757s across the Pond.) If there's a choice, AMS is an easier (and extremely efficient) airport for SkyTeam connections than CDG, although it's been improving. On DL and KLM flights, you can purchase EC seats with more recline and legroom (and free alcohol on the DL flights) for a moderate fee in addition to any coach fare. If she's flying coach, look for aircraft with nose to tail AVOD and nice seating arrangements. General consensus has been that the DL A330s are the best in the fleet for the coach experience, although the reconfigured 767s (those with 1-2-1 flat bed seating in BE) do have AVOD at all seats and the 2-3-2 configuration in coach means few middle seats. You're unlikely to find 777s or 747s to Europe, although IIRC DL uses the 777 for their JNB route; it's nice and new and does have AVOD throughout.

Needless to say, check requirements for passport, visa/work permit if getting paid, health (such as yellow fever card, tetanus and hepatitis shots, or malaria pills, both advised and required), health and other insurance, and be sure daughter has adequate credit cards for emergencies. The wildlife reserve is likely to provide this information to volunteers and will probably have additional requirements such as a health exam; they might provide some insurance too, so be sure to read their materials carefully.

This sounds like a very interesting opportunity for your daughter. Will she be able to share her adventures via Skype? Have you thought about what smartphone, etc. would make sense where she is going?