Student or Learner
1- She always complains about her little sister!
2- She complains always about her little sister!
Sentence 2 means that it is her little sister, nobdy else, that she always complains.
Sentence 1 could also mean that but it depends on the emphasis and the context. Right?
Sentence 2 doesn't work for me. I would probably always use the form in sentence 1.:
She always runs to work.
He always misses school.
They always complain about the state of the railways.
I always want to know more about a subject.
(BrE first language speaker.)