How can a girl be friendly with you and suddenly just ignore you?

we got along fine for like three weeks and suddenly from this weekend she stopped texting me. i sent her two texts asking her if she's ok and if she had a good weekend? no reply. her phone is working properly cause she called someone i know. in todays message i asked what she's up to and if her weekend was great. i dont think thats offensive. im not bombarding her with texts or anything. why would she ignore me. is she silently telling me to **** off and she doesnt want to be my friend?