Knowing whether a girl likes you is difficult at the best of times, so when the girl in question has a shy disposition, too, it can seem almost impossible to know whether she is interested. Shy girls tend not to openly show their true feelings at first, so instead you will have to look out for signs that she is into you.
Everyone reveals things about how they feel through their body language, whether they intend to or not, including shy girls. Next time you are around her, pay attention to whether she starts blushing if you speak to her or look at her. Does she fidget or play with her hair? These are signs that she likes you. She might also fix her shirt or flick her hair back as she approaches you if she is into you. She is trying to look her best for you.
Another telltale sign of whether a shy girl likes you is if you catch her looking at you and watching you at any opportunity she gets. Observe her out of the corner of your eye to see if she keeps glancing in your direction, and when you look back and catch her eye she will most likely turn away and try not to reach your gaze if she is interested in you. The shy girl wants to look at you but is too shy to make eye contact and let you know that she is intentionally watching you.
If a shy girl likes you, she will be nervous when she is talking to you. She might giggle a lot or stutter when she speaks to you. Or she might blurt out random comments or ramble on about something because she is nervous and doesn't want there to be an awkward silence. She might also avoid talking to you face-to-face and instead send friendly text messages, e-mails and handwritten notes.
Another way to tell if a shy girl is interested in you is to observe her friends and how they act around you. Although a shy girl might not tell you how she feels, it is likely that she has told her friends and so they will be keen to know whether you feel the same way, too. If her friends watch you and giggle and smile at you, it is a sign their shy friend likes you, especially if you catch them doing it while you are in the company of the girl in question. They might find excuses to find out more about you, like if you are seeing anyone, what your interests are and what kind of girls you like. This is to help their shy friend, who hasn't got the courage to ask you herself. You could use this opportunity to ask her friends a few things about her, too, and ultimately gauge whether your suspicions are correct and she really is interested in you.