Wsrtjtyk

If the pill contained a harmful or noxious substance, this is battery, which is a crime in Lousiana ("the intentional administration of a poison or other noxious liquid or substance to another"). There is a specific crime in LA, battery of a teacher, which is dealt with somewhat more severely than non-teacher battery.

It is not a crime to observe a crime being committed and not warn the victim, but it is a crime to aid the commission of the crime (for example to help the perp remove the lid, to supply the drug). Under section Title 17, a teacher battered by a student can file a school-system internal complaint which may lead to the student being expelled (this is ultimately covered by district-specific procedure). This is independent of criminal charges.

I told the school resource officer that I wanted to file charges
against her and he said all she'll get is a "citation" because it
isn't actually "criminal".

The school resource officer should be fired for jumping to inept conclusions instead of bothering to conduct at least a minimum of legal research on this. It would have taken him less than 20 minutes to realize that RS 14:38.1 sanctions with imprisonment the intentional mingling of harmful substances with someone's drink.

What about the other 21 students who saw what happened and did/said
nothing; just watched me ingest the medicine? Are they not
accessories?

Yes, they are what Louisiana law would call accessories after the fact. They might be sanctioned under RS 14:25 if it can be substantiated that their silence/concealment implies their intent that the girl who mingled the substance "escape from arrest, trial, conviction or punishment." (emphasis added).

Edit 11/13/2018

Yes, I'm aware this answer does not address "what are the legal ramifications"; it is rather an overview of what the OP should consider doing in order to protect her case and herself from the misconduct of the local school and law enforcement authorities.

You need the school authorities, police department and prosecutor to take you seriously. Tell the principal and the school board you are looking for a lawyer, and then find one; look in the phone book or online for a personal injury lawyer who gives free initial consultations.

Finding a lawyer will cause the board and school district to take you seriously and properly charge the student and take some sort of disciplinary action against the rest of the class. Since all the kids are talking about it, the school also needs to make a general announcement to the school and the parents that these types of actions are illegal and will be punished.

Write down what people said, the date, and time if possible; keep any papers and emails. Don't say you are going to sue or press charges; let the lawyer help with those decisions.

The lawyer can also talk to to the local city/county prosecutor to see what is appropriate in terms of the relevant local and state criminal codes for youth offenders. You would consult with the lawyer and the prosecutor about encouraging the student to be charged with a crime, i.e. battery of a teacher, as pointed out by user6726 in his answer: RS 14:34.3 - Battery of a school teacher : Louisiana Laws.

You could also file suit against the school for damages, but you may not need (or want) to actually do that if the lawyer can make enough noise so that they will take the situation seriously. But don't threaten a lawsuit; let the lawyer deal with that. Depending on what the school board and district does and doesn't do, you could take further action in terms of suing for damages; that would be under the advice of your lawyer.

Whether you choose to press charges is up to you, and not to the school. If you do though, make sure you have copies of all evidence relating to the school investigation and the student's suspension, in case it happens to "disappear" and everyone loses their memory.

I think the other answers are off-base to the extent that they assume that what the student put in your drink is "noxious," "harmful," or "poison." As you describe it, they put herbs in your coffee, and I don't think that in most cases, one could accurately categorize a commercial herbal supplement as poison. Even if you had special circumstances that made you allergic, I suspect that would only mean that you were particularly vulnerable -- not that the pill was poisonous.

I think a better fit would be RS 14:59, the criminal mischief statute:

Criminal mischief is the intentional performance of any of the following acts:

(1) Tampering with any property of another, without the consent of the owner, with the intent to interfere with the free enjoyment of any rights of anyone thereto, or with the intent to deprive anyone entitled thereto of the full use of the property.

The status of the other classmates is not clear. Louisiana puts participants in crimes in two categories: principals and "accessories after the fact."

Principals are the ones who do the act, help do the act, counsel others to do the act, or procure someone to do the act. If there were students serving as lookouts, egging on the students who put the chemical into your drink, or otherwise pushing the events toward the commission of the offense, those people would be considered principals and would be criminally liable.

Accessories after the fact are those who "harbor, conceal, or aid" an offender to prevent them from being punished. Simply failing to report the crime is typically not enough to trigger accessory liability, nor is refusing to snitch when asked. Affirmatively lying may be enough.

The circumstances here sound serious enough, though, that you should probably consult a real attorney -- maybe through your union, or through an employee-benefits plan -- to go over the specifics and answer the outstanding questions that will lead to the best outcome for you.