Just a guess: you might actually be running the CPU at a low frequency. As in the frequency scaling driver isn’t working.
Maybe poke around on a performance monitor tool. Seems like there’s “Plasma System Monitor” on KDE. Make sure the tool can see all the RAM, all of the CPU cores (2x physical cores with Intel hyper threading).
It should also report the CPU frequency, which should go up and down depending on the load. You can also check that the CPU temperature report is reasonable.
This also gives you process info, so when one of these 5 second freezes happens, you should be able to see what shoots to the top of the list. Or maybe there’s a background task churning through a bunch of stuff. Or maybe the flash access is really slow.
It matters a lot whether she is a US citizen or not.
If she’s a citizen, then she can shut up / lawyer up. She has a fifth amendment right to not divulge a phone or computer password, code, pin, or whatever. CBP can detain her for up to several hours, but at the end they have to either charge her or release her into the country.
If she’s not a citizen, then things are a lot tougher. She still has constitutional rights, including the fifth amendment. But CBP has a lot of leverage, because they can rule her inadmissable. Once that happens once, then it can become really hard to get readmitted later, because this “strike” is on your record.
The main thing that is tripping up green cats holders at the border currently is old criminal records. That DUI or marijuana or shoplifting charge or conviction from 20 years ago is often not enough dirt to get an LPR deported, but it is enough dirt to deny readmission if they happen to leave voluntarily.