Technically, your aunt could file a custody action against you, but she would have a very hard time being successful. If this were an action between parents, then the court would consider each parent having equal rights to custody of the child. However, since she is a third party to the child (not a parent), she would have a higher standard to overcome to obtain custody from a parent.
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She could file for custody. However there would be a significant number of hoops to be jumped through in orde for her to obtain custody based on the provided information.
Based on what you wrote, it sounds like you and your husband are good parents even if your aunt disagrees with your parenting styles. That is not enough for her to have custody of your daughter. A relative having custody usually comes about because both parents are unable or unfit to care for the child. From what you have said, both you and your husband are involved and there is nothing to say that you are unfit.
If she were to file for custody, there would have to a hearing before a Judge to determine whether she should have custody. (You can agree to her having custody but that does not sound like what you would be willing to do.)
It would take unusual facts for an aunt to take a child away from parents, so I don't think you should worry unless she files something. Obviously if she does, hire counsel at that time.
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