What to do if I like a girl, and she really likes me, but her intensity kinda scares me.

You can tell by the way her eyes and face light up when she sees me or I enter a room. She has told me outright that she likes me and we flirt back and forth, but sometimes her intensity scares me and makes me nervous. I do like her quite a bit, but i'm kinda shy and get nervous. What should I do?

Tell her she is, what you want her to be. Every time she does something in a calm relaxed way, compliment her like, "I really enjoy hanging out with you when it's calm like this. I'm just not in to panic." She'll get the message.

Don't let your shyness keep you from running your own life. You should never feel nervous about respectfully telling someone to back off for any reason.