This can't be normal?

My friend says that when she has a crush on a guy, she's a lot less talkative to him to the point where her bubbly personality disappears. But she seems to have bursts of confidence around him where she can talk to him normally, and even when he speaks to her sometimes she doesn't respond because he makes her nervous even If he only says "Hi" but she always looks at him, and Is hyper aware of his presence. Is this normal or Is this strange?
This can't be normal?
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