Three days not to contact her isn't ok. Personally, I'd be bummed at that. Long distance is hard enough. If you like her, id suggest making more effort into talking to her. As a girl, also in LDR I would be happy if we didn't talk for 3 days. She is starting to look elsewhere by the sounds of it. Communicate with her more. Also, sadly, I don't have the answer because I am not in her head, or know her. I think however, the lack of contact is pushing her to look for attention elsewhere.