I've bodyguarded 12 African Safari (220 days in the bush with 0 casualties to clients or their staff) but the magic of Africa lures me back! Botswana is the 2nd safest country in Africa after Namibia but Capetown has some safe areas and unsafe areas. Walking around there with a camera bag is NOT a good idea just like there are safe and unsafe parts of San Francisco or any other US city so I would suggest a small, unobtrusive point and shoot for there and to stick with her group. I agree with the other posters about NOT changing lenses in the field and to get a second OMD body. A "bean bag" is very useful for wrist or elbow support when shooting from a vehicle with lots of other photographers moving around. The Delta is magnificent but she really needs to be careful at night so a small strobing high intensity, 1,000+ lumen flashlight is useful. There are over 35 known poisonous species of snakes in Africa so the constant beam flashight is useful for detecting them. I raked the sand around our tent in Botswana so when we returned from safari, the staff had left the screens open. I tracked 2 snake trails going into our tent. I beamed under our beds and two cobras were using it as a honeymoon suite. I let the staff deal with them. I beamed the brush from our dining room area to our tent another night, saw 2 eye reflections, hit the strobe and the leopardess who was waiting to ambush us fled. I've also used a strobe to scare off hyenas and baboons at night. Africa is NOT Disneyland's version of wildlife. To put it in perspective, I've had 1.6 billion seconds of enjoying Africa and only 10 not so safe seconds.
Pay attention to the BEST and usually the oldest guide in your camps.
Lens hoods and good UV filters at all times will help. Sometimes polarizing filters are useful. Good lens brushes are useful since canned air may or may not be available in Capetown when she first lands.
Before she goes, "a journey of 1,000 miles begins with one step", towards her doctor for an arm and butt full of shots for her specific areas of operations.
Powdered electrolyte solutions, sun screen (applied 30 minutes before going out) microfiber, ventilated blouses/shirts, a decent brimmed and ventilated hat with a chin strap, polarizing sun glasses (I always buy inexpensive ones from Cost Co and give them as gifts to our guides who really appreaciate them) Lightweight parkas with hoods are nice for the rides in the morning and at dusk.
Keeping the photographer safe is even more important than taking photos so pay attention to your guides.
Hang on for dear life in your vehicle when animals don't obey the "rules of etiquite" about leaving people in vehicles alone, having been charged 3 times by elephants, 2 times by hippos and 2 times by lionesses, where our quick thinking guide drove away but on one escape, a leaf spring was broken and 2 tires were punctured by thorns which made for a wild ride and a need to use the bush as a bathroom facility afterwards, which is NOT a good idea so don't go far and get back to your vehicle as soon as possible.
Still, I'd go back to Africa...its that magical.

I went on Safari two years ago and still to this day my heart is in Africa. I took with me two camera's. My Rebel T41 with the Tamron 18-270 lens. I had ordered the Canon Power Shot SX50 to carry along. Well after the second day of not getting some of the birds I left the Rebel back at camp and just used the SX50. There were 16 of us and out of that 14 had cameras. I was the only one when we got back that had the best close up photos. I would go light and suggest that your friend get themself one of these. Also for Victoria Falls you will no have the worry of your lens getting moist in it. One of the group she did and her camera and lens had to be replaced. I could also handle it with out support and for the animals when they were running I found that the sports mode worked great. Also in Victoria Falls they have Walk With the Lions it was one of the greatest things I have ever done.

I just returned from there last month, unfortunately during the wet season this time. I have been lucky enough to go on three safari adventures in the past ten years. I agree with everything Matt from Palo Alto said. Also there were a lot of magnificent birds while I was there and my 400 MM lens was not long enough. In some (maybe all?) National Parks they are not allowed to go off-road so you may be photographing animals from very far off. We were in open sided vehicles (with canvas tops) exposed to everything including the animals. They say the animals are not threatened by the large vehicle and think of it as a larger animal. Move minimally, keep very quiet, keep yourself and your equipment inside the vehicle. Don't let them see you individually as prey. I saw a lion kill last year. They move so unbelievably fast. Also I would take two camera bodies with lens attached (one with my longest lens) while out on the game drives. If you want to see a lot of large mammals go during their dry season, not their wet season. Africa keeps drawing me back. At Victoria Falls I used water-resistant camera bodies and lens. Take the helicopter ride! It is so worth it! Have fun!

Did similar three week trip in 2013. Chobe game park, Botswana, Victoria Falls,Zimbabwe, Kruger National Park, South Africa , western Cape vineyards, Cape Town, cape of Good Hope, Table Mountain and botanic gardens. Changed lens often never had any dust problems. The walk along the Victoria Falls is often in high flying spray and the park provides ponchos. Worth the effort because of the often appearing rainbows ( I was there when the Zambezee was in full force and the spray could be seen from miles away) you have to do your best to keep the camera body dry - I shrugged under the poncho to achieve this without any downside effects.
I would suggest packing some ziplock bags large enough to put camera in and poking lens through the bottom - that way (in a wet/dusty situation) only the end of the ens is not covered.
Just be sure your friend takes plenty of memory cards. Probably only going to do such a trip once so shoot everything and edit once back home. I took over 5,000 photos and am still working my way through them.
Your question has pricked my conscience and I will try to post some of my better shots in the next week or so.
Your friend should have the trip of a lifetime. I would do it again in an instant were I able to.