Why do people text and then not respond?

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One of my close friends lives abroad, the first couple of years she moved out there we would keep in touch regularly, nowadays it’s less often because life. However this past year or so whenever she messages me she will ignore the response that I send to her and not reply?
Is this her way of saying the friendships over but she somehow feels obliged to keep in touch with me? Like I don’t understand why she bothers to message at all if she ignores my response?