I am really sad to hear this. These blood clots are extremely dangerous. My prayers for Tamar and her family. My mom had this same thing a couple of years ago. Thank God she is ok now. For the most part she felt fine. Until the pounding heartbeat started. This of course after the clot was in her lung. Blood clots are dangerous because there are either no symptoms or the symptoms are confused for something else. Obviously Tamar was sick. I bet she thought it was something else.
I am sure that Tamar thought she could go on, that is why she came back. It is possible that she was not informed about the blood clots until later in the evening or the next day. She might have left the hospital before the test results were back believing that she had some kind of cold.
In any case I am certain that she was not trying to cost Alexa anything. I am not sure how an extra week to dance compares to having a life threatening illness. Blood clots in the lung are no joke.