Rapid Heartbeat post Covishield-1st dose

After taking 1st dose of Covishield on 13th Nov 21, my sister got the common side effects of the vaccine alongwith a high fever, After this, she suddenly got a severe chest pain on 14th Nov (on the left side) which felt like a Heart Attack. Since then she is getting palpitations, has (abnormal) increased heart / pulse rate, shortlessness of breath, breathing difficulty, chest pain, unable to bend or lie down or even sit or do any activity, numbness in lower body. Can somebody please suggest the cause of this since she never had such issue before taking the vaccine. Also, please advice for some medication or treatment or cure for the same since it has been 1 month 12 days and the issue still under lies.