I disagree with your choice of charity but I support your line of thinking and your choices. The fact that this charity has numbers puts it way ahead of the slush funds that do zero good (or negative good). I personally think that's how EA will go mainstream, by encouraging everyone to make more quantitative decisions that result in more funding to better charities.
This person is also straightforward with their reasoning - yeah sure it's not as effective as malaria nets but it's a personal cause they care about. Most people don't even think about how effective the causes they support are - at all! It's mindblowing.
The trade-off is often not between charity X vs the most optimal charity, but any charity vs further consumption/savings etc.
Imagine EA ideas applied to fitness - sure some people may stick to a perfect routine etc but some people just getting off the couch and doing an activity they like enough to keep doing is best.
This person is also straightforward with their reasoning - yeah sure it's not as effective as malaria nets but it's a personal cause they care about. Most people don't even think about how effective the causes they support are - at all! It's mindblowing.