You seem to be making excuses for a lot of places which may take you out of your comfort zone. You want to go to S. Africa but don't want the cold yet NZ you don't mind the cold. You'd like to explore S. America but don't speak Spanish (with French and Italian you'll be able to get by fine, a lot better than thousands of tourists who go without any knowledge of Spanish or related romance languages), you want to visit S.E.Asia but heard it's not good for a single female (despite the fact that it's one of the most popular first-timer destination and thousands of young women head out there).
I think you should take the plunge and visit one of the above places. You say you don't want to do a tour, but maybe you should start off with a tour for a couple weeks just to ease you into the destination and get you feeling more comfortable before going off on your own. For instance consider starting in Victoria Falls and doing a trip from Vic Falls to Cape Town via Botswana and Namibia. Then you can go off on your from Cape Town. Maybe rent a car with some people you meet there and drive the Garden Route or get a Baz Bus pass. Eventually finishing up in Jo'burg. This would be a nice way to spend 6-8weeks.
Or go Ecuador and do a 2 week tour then fly to Lima and travel around Peru and Bolivia down to Santiago de Chile independently.
Or do a tour from Hanoi to Saigon and then continue through Cambodia and over to Thailand by yourself.
Given your single female, 22yrs old status know this. As a woman you do need to be more careful wherever you are than a guy would have to. But in the vast majority of places common sense will keep you safe. Don't walk down dark alleys in Quito at 3 in the morning or go flashing gold jewelery around J'burg or jump in a cab with some guy you've never met headed to a crack-den in Bangkok. Generally S.E.Asia is safe, a lot safer than most other places. If you go to Koh Pagnan to a full moon party then yes you have to be careful that your drink doesn't get spiked, but this kind of place attracts predators as it's full of easy pray high on drugs.
Enjoy whereever you go - if you do go to one of the three above destinations they're all brilliant places and once you push yourself to get out of your comfort zone a bit the next time will be easier.