What should I do in this Facebook dilemma situation?

[Vincent]

First set of problem:
I post something offensive under my sibling's status comment to defend her against some backstabber. It's not direct but catchy the type that gets the culprit's attention.

Second set of problem:
I had misunderstanding with my friend so its typical to watch each others back when it comes to status updates.

Problem:
She suspected me that my comment under my sister's status is referring to her which is not true.

Question:
How will I confront it? Should I apologize to her or explain myself over Facebook?

[pri✍]

You could message her to explain things.