My girlfriend of 8 months has started saying that she loves me. I don't feel the need to reciprocate that back everytime. She is getting pissed off at my Han Solo "I know" reply. She is now threatening to stop saying it because it hurts her feelings.

I'm not a validation pez dispenser. I think that saying "I love you" as often as saying "hello" destroys any meaning or weight. I'm also aware that this isn't about love, but wether I act like a good little bitch and do as I'm told. Any of you enlightened souls have some advice on how to handle this?