Ammunition acquisition is a real problem in Zim. There is reasonably well equipped gun store in Harare that stocks the more common calibers. As you know, he (or she) must have the rifle licensed in their name, which is not a big deal, especially for a PH. However, it is illegal to possess ammunition unless you have a registered, licensed rifle in that caliber.
If she can handle a .30/06, that would be my recommendation. It is a common caliber in terms of what clients bring, and while technically illegal, many clients will leave ammunition behind as an extra "thank you" to the PH.
I have never seen a 7-08 in Zim, but it is not uncommon in Namibia. You would have to check. I have a PH friend in Namibia whose son is deadly on Gemsbok culls with his suppressed 7-08.
I own a 7x57 and enjoy it a great deal. That said, it is not easy to find decent 7x57 ammunition in the USA. Don't know what the availability of 7x57 ammunition is in Zim.
The ideal situation would be if your PH handloads. You could bring the 7x57 and 100 rounds of ammunition (Norma 156 grain bonded Oryx) and a set of dies and that would serve her for a long time. The cases could be reloaded and that would keep her in shooting fodder for years. Ditto for the 7-08. Remember there is an airline limit of 5 kilos when flying with ammunition.
A Model 70 featherweight would be a good choice. The CZ550 is well understood in Africa, but I find it a bit heavy in the lighter calibers and sometimes they need a bit of action work to smooth them up. It is, however, quite rugged. There was a post recently here on the 'Fire that a dealer was selling Sako 85's for around $970.
