It happened before, it is happening now and

it will happen in the future. While I am ubable to judge who and what is wrong, What I can tell you is that if you keep fighting without concrete evidence, it will do you more harm than help.  When you alleged other people of wrong doing, you have the burnden to generate evidence, in your case, you cannot just quote what your boss "said", you need to provide recorded conversation to prove what your boss has said.  Without that, it is your words against her words.  Also, your statement 工作量是巨大的：我的同事失去了她的孩子. is groundless too.  Legally speaking, the event could have various reasons leading to it, you have to prove it is the work load caused the unfortunate loss, otherwise, it is not a case. 

The separation means that your company did not allege you of any wrong doing, they just wanted to terminate your employment "at will" which has been mentioned to you in the offer letter at the beginning of employment.

The lesson to learn is how to respond to an adverse working environment.