The 22-year-old actress, who cheated on boyfriend Robert Pattinson with the married director, has been texting Sanders, reported Showbizspy.
"Kristen is saying all the right things to Rob, but she is not being totally honest with him. Rob made her promise to stop talking to Rupert, and she has broken that promise already. Kristen justifies it because, technically, she is not actually talking to him, so she feels like she is still keeping her word," a source said.
"Kristen swears she is only keeping in touch with Rupert because she feels sorry for him. His wife, Liberty Ross, has totally turned her back on him, and Kristen feels somewhat responsible for that.
"She does not want to hurt Rob, but she does not see the harm in exchanging text messages with Rupert so that he doesn't feel so abandoned," the source added.