Ok, so here's the first thing--If you are a union hospital, do not, under any circumstances go into this meeting without a union rep. If you are not a union hospital, here's the thing. Go into the meeting prepared. You can prove that you are charting in real time, per the fact that they can check this. Additionally, I am assuming that when you informed your charge nurse that your patients were transferring, you documented this. If you did not, then I would from now on. However, back to present. You have proof that the improvement plan that was started for you is being done correctly. Hopefully, you documented "Charge RN aware" when your patients were being transferred. If they throw anything else at you, I would not say anything right away. Take notes. Let them know that you need the opportunity to review said notes, and ask for a break if you need one. Easier said than done, but do NOT get defensive, do NOT make excuses, do NOT threaten to quit. Just hear them out, present your side when you have had the opportunity to review--and listen to your union rep. if you have one.
If you can not financially make it without working, then to quit would not be in your best interest. If they are going to fire you, then you could have the option of unemployment until you find another position. (not legal advice, just a thought, and all states differ in this regard). Another thought process is to see what internal positions are available, and transfer. State that in fact you are not a good fit for the unit. DO NOT trash the management, the staffing conditions...that would not be in your best interests moving forward. Do not confirm nor deny, state you can only go on from here, state the obvious improvement in your charting, ask what the options are for informing Charge when a transfer is taking place in that moment, when Charge is busy with other duties and not hearing what you are telling her. State patient safety--this patient could NOT wait to go to the ICU until Charge was available to give you her full attention.
Meanwhile, look at your options. I would not rule out small community hospital ER's (which along with your Med Surg experience could put you in a better place for ICU if that is your goal) to do some per diem. Look at various openings of other hospitals in the area.
Best of luck to you. Remember, your character as a nurse is important. Your practice as a nurse is important. Don't put any of that in jeopardy by being unprofessional and letting anyone get under your skin at this meeting.