In order to determine if a statement is true (or rather, not false), we should use the most generous definitions we can. In this case, "white women" is the term in question.
To demonstrate "4% of the world is white women" without context is false, we must show no reasonable definition of the sentence is true.
We do have some context; the flags on the faces of the people in the picture.
The strictest definition of "white" I can find is "Northern European Ancestry" source.
For North/West Europe, I will use the populations of French, German/Dutch/Austrian, Scandinavian/Finland, Switzerland and from the British Isles, and people from that convex hull of nations, and the "white" colonies of Canada, USA and Australia.
This is based off a 1920s racist definition of white, but it is a definition.
The countries I will use are USA, Canada, Australia, UK, Ireland, Germany, continental France, Austria, Switzerland, Belgium, Netherlands, Denmark, Norway, Sweden and Finland, based off the 1920s racist "White" definition above.
The population of these countries in millions is:
318, 35, 23, 64, 5, 81, 66, 8, 8, 11, 17, 6, 5, 10, 5.
The sum is 662 million.
Roughly half of humans are female, so this makes 331 million female human candidates.
Now, another way to restrict what "white women" mean is to make "women" refer to "adult women" Source.
In the USA, 25% of the population is age 18 and under source. In the EU, 15% of the population is age 14 and under source. I'll use the average of these two (80%) to determine what percentage of female humans count as "women".
80% of 331 million is 265 million.
World population is 7.4 billion, so 265 "white" "women" is 3.5% of that total.
Now, not everyone from northern European countries or their colonies is "white" under this restrictive definition. source. So this means 3.5% should be multiplied by some unknown factor Y%.
On the other hand, there will be "white" people outside of these countries.
But 3.5% is sufficiently below 4% that this makes the above claims plausible, if you consider only adult female Northern Europeans to be "white women".