Article on the incident
There were service animals on the plane, the lady told staff that she was deathly allergic and asked to have them removed and (of course) was told no.
So then she asks for an injection which will allow her to continue because she forgot her own. They asked for her allergy card (something everyone with a deadly allergy knows you should always carry) to confirm so they could give her one, she didn't have it.
Southwest policy is that you will be removed from the flight if you inform them of a deadly allergy you aren't equipped to handle. They asked her multiple times to leave, then cops got involved, who also asked her to leave before the video started". - u/Kevinorhighwater
Looks like she got what she deserved.