Daughter & father again!

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My daughter (15 yr), is starting to say her father is a lier and that should had known by now! I know he is a lier (by ex. he is always coming with excuses to not pay all the support for his daughter to which he had agree in court, and i know there's no excuse at all), but never told her that or anything bad about him. i dont want her to get a bad image from her father, after all, "he is her father". The question is 1. should i say to her that in fact he is a lier and she just have to accept him like that? 2. Should i say to her that he is not a lier and to not talk about him like that? even being obvious to her? 3. should i say that once in a while some people, for some reason lie, but is nothing serious?