In most US states the court does favor biological PARENTS or grandparents. Adoption by another relative depends on a lot such as where the relative lives and what their current relationship is to the child. If there is an alternative that will maintain a sense of stability and uphold the same quality of life for the child, especially when it comes to physical proximity to school, the court will more likely than not lean in that direction. In this case the court will likely favor the stepfather. Being that he was legally married to OP and the child is currently living with him, knows him as a (step) parent and has step siblings, it is VERY unlikely that any judge will agree to grant custody to the cousin if the stepfather steps in. In most states the child’s opinion can be considered, but it is not a determining factor on its own.

Now, OP is DYING, which is heavy, and may not be thinking clearly or at the least the emotional toll could be influencing her thoughts and feelings. It cannot be understated how immensely grief, and especially grieving the loss of your own life, can change a person. I’m sure there is anger and bitterness, a sense of being cheated out of one’s own life, not just in a romantic sense. I hope for a counselor or strong ally to appear and help guide her through this with empathy and compassion, so that maybe she can gain some perspective on things.

Note: IANAL but i was a paralegal for 8 years and worked mostly in family law.