Word for "not putting thought into something"

The situation you're describing doesn't so much sound like she was putting no thought into her answers, as that she didn't want to have the conversation, and therefore was deliberately not engaging with the conversation, perhaps to send you a signal to stop talking to her.

This style of conversation would be described as dismissive

http://www.thefreedictionary.com/dismissive

perfunctory

adjective

1. performed merely as a routine duty; hasty and superficial:
   perfunctory courtesy.

2. lacking interest, care, or enthusiasm; indifferent or apathetic:
   In his lectures he reveals himself to be merely a perfunctory speaker.

[dictionary.com]