She had to watch that train disappear towards her destination while she was left behind.
依据主从句逻辑主语一致可省略主谓的原则能否改成:
She had to watch that train disappear towards her destination, being left behind.
不能。
She had to watch that train (disappear towards her destination while she was left behind).
这个状语从句是从属于不定式的。 Disappear的主语是the train,所以不符合你说的那个原则。
不过这个问题倒是挺有意思的。