Shaking may mean rigor?
Obviously, she has severe breathlessness
It may be a reaction to the flu shot - asthma?
It may be heart failure
precipitated by blood pressure, in this stress
The picture sounds ALARM bell - she has to be seen IMMEDIATELY by a doctor. Blood counts and cardiac markers; ECG; X-ray chest and so on are a must. No specific management is possible without clinical and lab work up.
Delay may spell danger.
Wishing her speedy recovery