I've been freediving for 20 years now and I've never heard of anyone (nor myself) having trouble reaching the surface because of currents. Strong currents affecting a freediver are lateral, not vertical.
Not trying to say currents are not dangerous for freedivers. I've friends who did end up lost for hours in the surface because of currents. Also, if you want to reach a certain spot in the sea floor and there is current you will consume more O2 and you increase your chances of blackout before reaching surface.
But dying because of being carried away? hmm no..
So, the only true thing is that she did black out and did not come to the surface. The current is the reason why they are not finding her. No one will ever know why she blacked out.
edit: typos