MILF-(slang) Mother I'd like to fuck: A (putative) mother found sexually attractive.
This is what MILF means, please notice the main word in there is "I" meaning me or who ever says the word. So that means if I say you are a MILF doesn't mean every guy on the planet thinks you are one. Also that means if a guy calls you a MILF doesn't mean you are one to me. It basically has the same meaning as the saying "Beauty is in the eye of the beholder"