Antihistamine may help if there is an allergy present. Crown it self is not like an allergen. I personally do'nt think removal of crown is beneficial.
Do the teeth need to be removed if it's an allergy? Or will it go down with time? What should she take for the swelling in the mean time? If the crowns need to be removed what happens then?
The dental material used during crown delivery are probably luting agent (cement) and articulating agent, which rarely are associated with allergic reaction. Acute swelling of tongue and lips may be caused by allergic reaction or air entrapment coming from handpiece. If the luting agent is temporary cement, which may contain zinc oxide eugenol, few pateints are allergic to. If the swelling is caused by above causes, the swelling tends to subside within 48-72 hours. if the swelling is caused by infection, investigation of the source of infection is warrented. Going back to her dentist to have a through evaluation is advised.