Her choice is between a dizzy head and a heavy heart (4)
I believe the answer is:
dora
'her' is the definition.
'choice is between a dizzy head and a heavy heart' is the wordplay.
'choice' becomes 'or' (I can't justify this - if you can you should believe this answer much more).
'is between' indicates putting letters inside.
'head' suggests taking the first letters.
'and' is a charade indicator (letters next to each other).
'heart' says to take the centre.
The middle of 'heavy' is 'a'.
The initial letter of 'dizzy' is 'd'.
'd'+'a'='da'
'or' going inside 'da' is 'DORA'.
Can you help me to learn more?
(Other definitions for dora that I've seen before include "David Copperfield's 'child-wife'" , "Bryan" , "This girl" .)