hi depressed,
a vital component of long distance relationships is effective communication. it is important for both parties to be able to feel that if they need to talk or write to the other person, communication will be welcomed and met with active communication from the other.
on the other hand, if she wants to make herself more distant emotionally than she is geographically, then the easiest thing for her to do would be to shut-down communication. she knows you can't confront her physically so she has taken the lazy (and somewhat logical considering the circumstances) alternative of just not communicating.
i think her lack of communication is a huge red flag. paradoxically, i also think her lack of communication is sending you a very loud and clear message...but only you can find out for sure.
while none of us here can say whether she's a sadist or if she's being defensive, i tend to lean towards the idea of her being just plain chicken and wanting out of the relationship without actually having to confront you...which of course would mean communicating.
i think it's up to you to grab the bull by the horns and just flat out tell her to come clean with her feelings. to not communicate will only delay the inevitable, if it is indeed the inevitable. if she refuses to communicate, then it probably is the inevitable. long distance relationships need honesty too.
best wishes