I'm going to reject a gift my girlfriend was making for me
What gift did your girlfriend make for you?
Its a teddy bear my girlfriend made for me with her own hands.
A gift is an extension of a good thought of someone, so denying that, whether you like it or not, is just rude. Most people consider it polite to tell small lies about gifts rather than telling the giver you are disappointed.
I'm not going to lie about how I feel about her gift.
It'll hurt your gf's feelings so if you want to maintain your relationship with her you should be polite and grateful for the gift. It doesn't matter whether you like it or not, as a boyfriend you should accept it.