I'm not reading the article but off the cuff I'd give 2 reasons:

1 - her doctor is fucking based and is giving her a HDQ + Ivermectin conctile each an every time for therapy and she beats it within days each time.

Or

2 - the tests gave her false positives due to the over samples / over cycling problem proved in recent studies where tests are being sampled up to 90 times (engineering requirement is only 25 to 30 cycles) and thus they're over representing residual viral material and never smd actual infection.