Factual error: Opening the blank envelope, Marta finds the fragment of the toxicology report. It is signed "Office of the chief medical examiner, Norfolk County, Massachusetts." But then it writes also the address of said office, which is in Marlborough. Marlborough is also the city when Marta resides, and where the lawyers' letters we see come from. But Marlborough is also a city in the Middlesex county, not Norfolk. (01:28:25)
Factual error: The damning vials of medication are in close-ups. It is printed on the label that we're talking about 20 ml vials. The morphine vial is 5 mg/ml. When Marta says that she gave Harlan 100 mg of drug she is then wrong; unless she administered the full vial. The two vials have in fact different concentrations: the Ketorolac is in a 30 mg/ml solution, so Marta would have administered 600 mg of ketorolac tromethamine, not 100. The maximum dose for a geriatric patient is 60 mg per day; even the fact that she'd administer it in IV for days for just a pulled shoulder is definitely overdoing it anyway - and she puts even morphine on top of that. (00:36:00 - 01:49:00)
Factual error: The drug in Marta's bag is incorrectly labeled as Ketorlac, when it's Ketorolac, with an extra O. It's the name of the molecule, not a brand name that could have been altered for legal reasons - and they mention the commercial name just minutes later during questioning, with no alteration. (00:36:00 - 01:49:00)
Answer: To add slightly to the other answer, evidently some of the blood in the scene had to be digitally removed for the film to secure a PG-13 rating, which explains why we don't see any actual spray/gush. But we are to assume that a drop managed to splash onto her shoe when he slit his throat.