How can you tell if your girlfriend really loves you or not?

You can't. However, trust is a key component of love. If she tells you she loves you, you have to trust that she really does love you. The best thing to do is communicate with her, and find out what she thinks and feels. Also, your feelings will effect how she feels, so make sure you are honest with her as well. Good luck!

Not true,

If she has any chance to go with you or sit by you, then that is a key sign. Other signs are examples below

If she texts, e mails, calls you a lot, that means she is thnking of you.