Re: Two Pakistani girls. Two very different stories
Brother, funny but interesting question … I think you should write to Pakistan defence ministry to get your answer … and by the way, at present Nawaz Shareef is not only Prime Minister of Pakistan but he is also defence minister of Pakistan … so regarding question you have in your mind, Nawaz Shareef (Prime Minister as well as Defence Minister) is most likely person to know and answer.:).
Anyhow, even though I would not know as I am not ‘defence minister of Pakistan’, I can make a reasonable calculated guess 
Pakistan has one of the biggest and considered to be amongst the best intelligence network in the world (ISI is considered as world number one intelligence agency), with lots of people working at ground level. ISI, Local administration and other relevant government organisations know most of terrorists just like police know criminals in their area. All terrorist organisations in Pakistan have intelligence agency’s planted men within them. Pakistan intelligence agencies also have means to tap into conversation terrorists do with each other using any sort of media tools. That is the reason, most of time, Pakistan intelligence agencies gives accurate warning to government about Taliban and other terrorists planned attacks … and at times can even tell movement of suicide bombers.
What I believe, it is Pakistan intelligence that sends information along with co-ordinates to USA about terrorists’ whereabouts, giving direction regarding ‘time and place’ to hit them terrorists with drones. Once target is hit, intelligence agencies start collecting information about casualties … who died and what was their role in terrorist organisation. Even though most of the time intelligence agencies keep quiet, but sometime they do leak the information and that is the reason when Hakeemullah was killed, Pakistan media was first to declare that he got killed (at that time, neither Americans nor Taliban were admitting that Hakeemullah got killed).
Actually, it is no big deal for Pakistan intelligence agencies to know the casualties after each drone attacks and involvements of the person killed/wounded in terrorism. Pakistan intelligence agencies report to chief of Pakistan armed forces, as well as defence ministry, so for defence ministry to know who got killed or wounded, and what was their role in terrorism, is obvious. Leave Pakistan, intelligence agencies of most countries would know such information if any killing is happening in their country.
Thus, one can safely say that no one in the world could accurately know as much about the people killed in drone strikes then Pakistan intelligence agencies, Pakistan armed forces, and Pakistan defence ministry. Since Senate asked, they came with the figures.