I tried finding it but I listened to someone on KQED/NPR who worked for Obama's White House and had to go through a security clearance. She said she used marijuana hundreds of times, and they let her get the job. Something doesn't add up. Or, for your friend's specific job they had different rules. She wasn't an intern or something very low level, but I can't remember her title. Edit: Deputy Chief of Staff for Operations, so pretty high level.
Edit:
Found it https://www.npr.org/2018/03/30/598253244/i-basically-ran-on-...
"GROSS: (Laughter) Right. So I thought this was really interesting. You had to get national security clearance for your job.
MASTROMONACO: Yeah.
GROSS: One of the questions you had to answer was a kind of detailed list of your drug use. And you'd smoked marijuana.
MASTROMONACO: Yes.
GROSS: You had to say how many times (laughter).
MASTROMONACO: Yes. That was...
GROSS: Yeah. So you handled it by saying unknown. How did you come to the conclusion that that would be your answer, an unknown number of times?
MASTROMONACO: Because - well, because I really feel strongly about not lying. And so when the FBI agent asked me for a number of times and she said, you know, 20? And I was like, no. She said, a hundred? I said, no. And then when she got up to 500, I was like, I'm not saying - I'm not giving you a number because who knows if they're going to go try and prove the number? So I just said, unknown. And apparently from her reaction, nobody had ever said that before.
GROSS: You write that you had to get randomly drug tested almost every month. Is that because you'd said unknown or does everybody have to do that?
MASTROMONACO: No. Most people get drug tested, like, once or twice that first year. But I was drug tested quite often because I was very forward-leaning about my drug use, very open-kimono, as we would say. And so, yeah, every - just about every month, you'd get an email that said, you know, you have 24 hours to show up for your test. And I would. And it was fine because I wasn't. So I had nothing to hide (laughter)."