She got nervous and tongue-tied when I approached her?

So there's this girl who's had a crush on me for over a year now, and I finally approached her a few days ago. When I was walking with her and asking her questions, she simply gave yes or no answers and didn't seem comfortable. She got tongue-tied when I approached her. With other guys, she's always open and outgoing, but it was the opposite with me. I kept talking to her like a friend though, pretending like I didn't notice her nervousness. I will approach her again soon, but have a feeling she will still be tongue-tied and nervous. How can I get her to start being more open with me? I'm making sure I'm really friendly. Will it just take time for her interactions with me to get better? Any advice?
She got nervous and tongue-tied when I approached her?
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