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 explain this - if you can you should believe this answer much more).
'is between' indicates putting letters inside.
'head' suggests taking the first letters.
'and' says to put letters next to each other.
'heart' indicates the central letters.
The middle of 'heavy' is 'a'.
The first 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" .)