I think this one is obvious, but shy girls blush, a lot, especially around their crush. Personally, I can't help it, whenever i'm around my crush, I blush like crazy. My face literally goes from pale to red. It's so embarrassing, but also very true.
2. Staring, but not talking
I am guilty of this. I stare at my crush, but never talk to him. I feel so nervous that I could faint if I ever did go to talk to him. So, I stare. A lot. And sometimes he stares back, which makes me blush a lot and makes me even more nervous around him. But yeah, shy girls stare, but don't talk to their crush
If a shy girl doesn't usually wear makeup (like me), then she will wear it around her crush. I just feel like I would be more attractive to him if I wore makeup around my crush. Which may or not be true, I don't know, but that's just how I feel. I like the natural look usually, but I want to impress my crush, so I wear makeup.
4. Ignoring you
I am so guilty of this myself. I know, ignoring your crush isn't exactly the greatest way to show him you like him, but I do it anyways. Shy girls just feel too nervous to talk to their crush. And we overthink, all the time. So, we ignore the guy in favor of embarrassing ourselves.
5. She sticks close to you
So, yeah she will go where you go. It's so stalkerish, but it's still what we shy girls do. I know that sometimes I walk closer to my crush if he was standing somewhere with his friends, but I would still keep my distance from him.
6. Facebook stalking
Yep, we facebook stalk our crushes. We might not even send you a friend request, instead we just keep our eyes on your account to see what you're up to. We can't help it, we don't talk to you, so we need to know what's going on. Are you going out with someone, do you like someone else, etc...
There are other signs too, but i'm just pointing out some of the things that I personally do. So, if you have anything else to add, feel free! =)