I have concluded those test are complete crap.
Everything sets them off, Ibuprofen, Tylenol whatever.
Tell your mother they are junk.
GC-MS is the only legal way to prove you have something in your system.
The antibody test (home test are anitbodies) are just screens and not worth a damn, they are easily beaten and come up with false positives all the time.

Any real lab uses Antibodies for screens and confirms with GC-MS so they dont get their asses sued off.