I am investing in real estate in South Africa and my gf's parents will be handling the finances there in South Africa. I need to wire transfer $80,000 to them (bank to bank).

Question is do I have to tell IRS I am sending $80,000 to South Africa?
Do I have to pay taxes on that $80,000?
Is it better if I wire $40k and my girlfriend wires $40k?

Question is do I have to tell IRS I am sending $80,000 to South Africa?

No.



Do I have to pay taxes on that $80,000?


No, at least not in the US. I don't know how South Africa treats incoming international wire transfers.



Is it better if I wire $40k and my gf wires $40k?


Doesn't matter, at least not from a US tax perspective.

Agreed; there are NO transfer taxes for the United States, and the transfer amount falls BELOEW the $100K threshold for filing Form 3520.