My ex girlfriend liked my Facebook picture... why?

We haven't talked from 3 months. A month before she called me I didn't pick up. After I haven't heard from her. It's been a month. But yesterday she had liked my Facebook profile picture.

Can anyone tell me what does it mean?
Updates
+1 y
After a month I again changed the pic she liked it again...
My ex girlfriend liked my Facebook picture... why?
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