I think that people who can't accept compliments because they don't believe them are pretty common in therapy. And I don't think your reaction is not useful...she's seeing what you really think about yourself and how it's hard for you to take in positive information about yourself.

And I second what Hankster said about you being able to tell your therapist what you're feeling...good job! I react the same way but instead of saying "back off, you liar!", I look at the floor and feel uncomfortable when t says nice things about me...