Search on Facebook

So, there is a person with whom I am not a friend (we have 8 common friends), and almost every time I look for it, the result is different.
For example:
The first time I looked, I saw that she had posted 3 posts on the wall of other friends.
Second time, there was only one post (I am friend with the person on whom she posted)
And the third time, there were no messages.

So, people, where she posted did not change the confidentiality of the publications, so why do I sometimes see publications and other times?