Most likely she was cleared years ago when she was not radicalized and has not been up for clearance renewal during that time.
She most likely lied in regard to the pledges of loyalty originally required to obtain her clearance.
That's debatable.
Don't confuse clearance with background check. I was a linguist in the Air Force, as well. I've been out for more than 20 years, but it still works pretty much the same way.
When we first enlisted, we got a comprehensive background check for the clearance level needed. There are multiple levels of clearance, depending on the job to be done.
My first 14 months in the Air Force required absolutely no clearance level besides a basic background (criminal/financial) check that everyone entering the service went through. This got me through Basic Training and the language course at the Defense Language Institute (DLI). By the time I graduated from the DLI, my comprehensive background check was completed, and I was granted the appropriate clearance for my second-level training which occurred at Goodfellow AFB in San Angelo, TX.
When I left Goodfellow, to go to my first actual duty assignment in Korea, I was debriefed from my clearance at the training school, and my clearance was temporarily suspended until I reached my duty location. I was not allowed to enter any classified facilities until my clearance was re-instituted at my formal duty station. The same thing occurred when I left Korea for my next duty station at Davis-Monthan.
I was debriefed, and clearance was suspended.
I got my five-year follow-up while I was stationed at Davis-Monthan.
While I was at Osan AB in Korea, I was originally assigned to come back to Fort Meade, MD, to work at the NSA. That assignment required a deeper investigation (not sure how, because I was only 18 going into the AF, and I'd been theirs for 2.5 years at that point), and a Polygraph examination, which I passed.
Eventually I passed on that assignment, stayed in Korea a second year, and then got the Davis-Monthan assignment, which did not require a Polygraph.
When I processed out of the Air Force after just under seven years (had to extend my original 6-year to get to D-M, as they required 3 years retainability), all clearances were revoked, and I was basically given the paperwork saying there was a lifetime ban on me talking about anything classified from my job, under severe penalty.
My background investigation was still good if I wanted to go civilian, or re-enlist, but my clearance was revoked.
Usually, there is supposed to be a follow-up investigation prior to hiring on anywhere else a clearance is required to cover any period between exiting the service and being hired into the new job.