That girl who's always scheming behind my back at work

Hey girls, I'm really frustrated about something. There's a girl in the office who constantly takes credit for my work and presents it to the boss as if it's her own. Today, during a meeting, she literally explained my idea as if she had come up with it. I was shocked and just stared at her. I mean, can a person be this shameless? What should I do about this girl? Should I talk to her directly or just ignore it?