Flight attendant reported a fume event; illness; and having to return to the gate.

Narrative

During Taxi; the Captain advised our taxi time would be longer than usual due to congestion at the ZZZ airport and a closed runway. Shortly after the Aft galley was filled with a noise that pierced the ears but also sounded like the APU was attempting to start up. This sound was longer and louder than usual. So much FA2 [Flight Attendant two] had to cover her ears. Approximately 4-5 long roars of a whining motor were followed by a strong tart and sweet odor that stung the throat and eyes. As the odor continued; FA2 proceeded to get up from jump seat and retrieve napkins to cover mouth and nose. FA2 returned to jump seat and felt light headed; headache; stinging throat and nausea. Upon arriving at gate FA2 was barely able to get up to disarm doors but was able to and communicated during all call that there was a strong odor and that they were felling sick. FA's 1; 3 and 4 agree with FA 2 that they can smell a strong odor in cabin as well. The recollection of what happens next is patchy as FA only remembers feeling twitching on face; chest pain and tightening as well as throat irritation. FA2 calls Captain during deplaning and advises that they are not feeling well and that the odor present is sickening. Captain advises to move; FA2 is unable to and Captain asks if FA2 can reach the oxygen bottles. FA2 asks passengers for assistance reaching the bottles behind the last row and dons the supplemental oxygen in jump seat. FA was unable to leave immediate area with passengers in the aisle. After deplaning was done. FA1 walked back and saw the condition of FA 2 and asked the Captain to call Paramedics. After donning oxygen FA2 was assisted by FA 1 and 4 up to first class and waited for paramedics. Paramedics said they were not present for onset of symptoms and could not assist. FA found no procedure for what to do during taxi if odor is detected. The only definitive procedure written is to contact Captain and cover mouth. During taxi in while strapped in jump seat; lights off and unable to remove oneself due to deplaning was dangerous without breaking FAR. I had to getup during taxi as well as confused and disoriented disarm doors. My cabin lights were off far longer than usual due to being disoriented. I believe had procedures for checking for Crew incapacitation during and after odor should be part of the duties carried out during a fume odor incident. Procedures for fume odor events should be for all phases of flight and not just if you are on or off the plane.