Sara Carter is a Navy vet. Skye P. Marshall, who plays her, is also a vet in real life, albeit from the Air Force.
An Individual Augmentee is a member of the United States military, often with special knowledge or skills (like a doctor, nurse, sniper or EOD specialist), who is temporarily reassigned to a different unit to fill a vacant post that urgently needs filled. For example if a company's only surgeon is wounded or killed in action a surgeon from a different company, battalion, or sometimes even a different branch of the military, will be reassigned as a Individual Augmentee until a permanent replacement can be found. So for example a United States Navy trauma surgeon might be temporarily reassigned to a United States Army company.
Prescription medications that are Schedule II, III, or IV controlled substances (especially Schedule II drugs) cannot be sent through the mail directly to a private residence. They can only be mailed to a facility or residence (such as a nursing home) that is licensed and registered with the DEA (Drug Enforcement Administration). If someone is required to use a mail order pharmacy by their insurance and they are being prescribed a controlled substance they either have to get it filled at a local pharmacy, or have the mail order pharmacy ship it to either their doctor's office or a local licensed and bonded courier who is registered with the DEA. If it is being mailed to a courier then they must deliver the medication package directly to the patient they are prescribed to in person, they cannot just leave the package in the mailbox as was done in this episode with one of the veterans who had his pain medication stolen out of his mailbox. The courier would also be required to check the ID of the person accepting delivery of the medication to confirm that they are either the person being prescribed the medication or are authorized to receive it on their behalf.
Maria Bello while talking to Leon asks if not investigating the case involved principle. Bello co-starred in Payback (1999) where the main concept of the film involved the principle of getting what was owed to you and nothing else. The term principle was even defined onscreen in the director's cut version of the film.