Dr. Kumar is very busy with her practice. She has _______ time for other things.

'Time' is an uncountable noun, so we use 'little' or 'a little' (not 'few' or 'a few'). 'Little' has a negative meaning (hardly any/almost none), while 'a little' has a positive meaning (some). Since Dr. Kumar is very busy, she has hardly any time for other things - the negative meaning fits. Therefore, 'little' is the correct determiner.