A321 FA reported there was a fumes event during preflight that resulted in an aircraft swap. During the descent in the replacement aircraft; one of the flight attendants began to feel unwell and required medical assessment.

Narrative

Our No. 4 noticed a smell in back galley of burning plastic type odor. She went up to inform Captain. Later the First Officer came back to greet us and smelled as well told the Captain. Boarding starts. Towards the end of boarding and during the cabin preparation I can smell a little bit of the odor at Door 3. I told our No. 1 about the smell. Maintenance exited the airplane and explained over the PA that everyone has to deplane due to the odor. We switch aircraft; rebound the other aircraft. This in time took 1 hour and close to 30 minutes between the reported smell from the first aircraft towards the end of boarding to the second aircraft before a service manager at that time comes to the aircraft to finally check on us. Had to wait for Catering to bring over the catering supplies and equipment from other aircraft sitting at the hangar.At that point we leave for ZZZ1. During late cruise and descent in to ZZZ1 our No. 2 FA feeling some signs of headaches and not feeling well. She called the flight deck to explain symptoms. I had to relieve pilots for bathroom break at that time. I personally did not hear all the communication that was said but before landing the No. 4; No. 2; and myself were under the impression paramedics were meeting at the gate to take care of our No. 2 FA. We get to gate; no paramedics at end of deplaning. Our No. 4 was very concerned about our No. 2. Went to Captain to talk to him about it. At this point we are at the front of aircraft heading into the jetway when the Captain and our No. 4 got into a heated discussion. Our No. 4 was being very calm and trying to understand why paramedics were not immediately at the gate to take care of our ill crew member. The Captain got really defensive and started behaving towards our No. 4 in an unprofessional matter in the jetway in front of the Gate Agent and a few of the outbound crew members taking the aircraft back as well as myself and our No. 1. Our No. 2 at this time still not feeling well was on the phone with service manager. I witness the Captain raising his voice at our No. 4; saying he is going take this up to professional standards and well what happens I'm a senior Captain. I told the Captain do not talk to her like that and the way you are behaving is unprofessional. The paramedics finally showed up in the terminal gate area to access our No. 2's condition.Our Captain should've been more assertive in procedures as far as holding off boarding the first aircraft as well as checking on the wellbeing and health of the crew during the odor event on the first aircraft as well as having clear and better communication with our cabin crew during our descent into ZZZ1.