Suspicious, and worth further investigation.
1. Her test showed the the banned substance at 5 ng/ml
2. The science says that men eating 310 grams of the right kind of pork can test within the range of 3.5-7.5 ng/ml. Granted, she may not need to consume that much because of being lighter.
3. She said she ordered one kind of burrito but may have accidentally consumed the tainted pork burrito. How much pork could plausibly been in that one pork burrito? Half a pound? Did she eat more than one? If she pulled the wrong burrito out of the bag and bit into it and just decided to finish it, wouldn't she have been more careful about the next burrito? That's a lot of coincidences. Coincidences do happen, however.
4. And then, coincidentally, the test happens 10 hours after the burrito bungle. We're straining credulity, but still on the outer edges of Murphy's law of plausibility.
5. She apparently provided hair samples that shows no buildup of the banned substance, suggesting that she was not a long term user (or can this be faked or masked by microdosing? idk).
Apparently the testing authorities could have chosen to give the benefit of the doubt and continued the investigation, but instead decided that the evidence was conclusive enough to end her career. I might be wrong about that.
I'm not an expert, so maybe I'm missing something, but based on this evidence, I don't see this as conclusive.
And that's what bothers me. I think her burrito alibi provides reasonable doubt. But I don't know what the standard of judgement is supposed to be in these cases.