It is difficult to know if this girl likes you. There are some girls who are very affectionate with people. Do you know if she is like this with all her friends? If she does, then it isn’t sure that she is bisexual. The best to answer to these questions is surely to ask her but sometimes it isn’t easy to do it. If you are a shy person you probably don’t want to try this way. Furthermore, maybe this girl is not ready to do her coming out so she will answer no even if she is bisexual.
There is another way to have an idea of her feelings about you. Does she touches you more often and more longer than she does to her other friends? Does she seems to be embarrassed or confused when she is with you? Maybe she is more helpful, kind or nice with you than with others?
Is it because you like her that you want to know how she feels about you? If you do, you can tell her about your attraction to her. You also can offer her to go out with you to see a movie, restaurant or to do an activity you both like. Then, it will surely gives you some opportunities to talk with her about bisexuality, relationship between girls, etc. This type of discussion will gives you a good idea of what she thinks about it and maybe of her sexual orientation.