Animals have been part of my life ever since I was a boy growing up on my father's farm, and I certainly can understand the strong affection some people have for their pets. I'm afraid I've also met people occasionally who seemed to pay more attention to the welfare of their pets than they did their spouse or children.
But, of course, that is wrong, because God gave our families to us, and they should be our first priority (next to God). The Bible says, "Husbands, love your wives. ... Each one of you also must love his wife as he loves himself" (Ephesians 5:25, 33). Pray for your aunt, and if you have an opportunity, gently share your concern with her. She may not even realize what she's doing.
Remember: If God makes us part of a family, nothing should come between us and our family responsibilities. Not only do we have a responsibility to look after each other's physical and emotional well-being, but we also have an obligation to help each other spiritually particularly as parents.
As a footnote, have you ever asked yourself why your aunt is this way? I don't know the answer, of course, but perhaps she's been hurt by people in the past, and simply finds it easier to deal with animals. Or perhaps she feels her pets give her more affection or appreciation than people do. Whatever the reason, pray for her, and go out of your way to show you care for her.