Quote Originally Posted by Throbert McGee View Post
(1) Here, "only" is adverbial, so I would use только (or лишь would work here too, I think), and place it immediately before the direct-object phrase:
I would ask a native speaker, but I'm pretty sure that you could also put мою at the end to emphasize it:
Кошка любит только сестру мою.
I want to add that if you add one more word and "-" sign:
"Кошка любит только одну сестру - мою." is "among all sisters only mine are beloved by this cat" without any doubts.

Quote Originally Posted by maxmixiv View Post
Только мою сестру любит кошка.
Intonation decides, but the sentence is such that the only normal meaning is "кошка любит только одного человека - мою сестру".
I disagree about "only normal meaning". But agree with ambiguity. Most normal order of words is "кошка любит только мою сестру". Usually if you reoder words to "Только мою сестру любит кошка" there is reason for it. One of them can be stressed "мою", but there may be overs.