AIO after what I learned about my cousin's child?

So yeah. This Christmas, most of my extended family came over, and for the first time in 11 years, my cousin "F" showed up.

Growing up, F was basically a sister to me and my siblings. Her mom worked abroad, so my parents helped raise her for a long time. We were close, but I know my older sister adored her the most, since they were both firstborn daughters and shared similar burdens. F went no contact with the entire family 11 years ago due to issues with her birth parents. I was especially hurt that she cut even my family off, because I believe whether she was right or wrong during that time, we would’ve supported her. Over time, I let it go. I figured she did what she needed for her own peace, and I respected that.

This Christmas, I was already anxious because my relatives love interrogating me about my life (dating, marriage, kids, grad school, etc.), and we weren't even expecting F. So when she walked in, it was honestly really emotional in a good way.

Then she surprised us again by introducing her child, "C."

Since none of us siblings have kids, we were thrilled. We spent the afternoon playing with C while F caught up with the family. Everything was so nice.

My brother brought out a children's book and asked C if she wanted to read it. She said no, not because she doesn't like to read, but because she didn’t know how to read.

We were all stunned. C looked around 9 or 10, but we hadn't confirmed yet. So I asked how old she was. She said she didn’t know. We asked when her birthday was, and she couldn’t remember if it was in June or July.

At this point, my siblings and I were completely confused, and eventually, my older sister and I went to talk to F.

The conversation started light. My sister joked around, asked how F was doing, who the father was, if she was in a relationship. F laughed and answered everything. We learned that C's father went out for milk in 2019 and F has been a single mother since, but more importantly, C IS 10 YEARS OLD, the age of a 3rd or 4th grader.

I mentioned that C said she couldn't read, hoping F would tell me her daughter was really bad at making jokes or something. But no, she just said, "She's more of a visual learner."

My sister carefully asked if C truly couldn't read. F waved it off and said C would learn when she was ready. She didn't want to "force" her because it could damage her mental health.

I asked what a normal day looked like for C. Lessons? Activities? Even just practicing writing her name? F shrugged. She works night shifts, so they mostly rest during the day. Sometimes they watch videos. Sometimes C plays on her tablet.

That "something is really wrong" look passed between my sister and me.

Then F casually mentioned struggling financially. Complained about exhaustion. And then, laughing, talked about online casinos and betting apps, joking about bad luck streaks and "almost winning."

My sister then asked the question we were both thinking: "Why isn't C enrolled in any school? Even public school?"

F immediately got defensive. She said school was expensive, transportation was hard, teachers didn't care, schools were far, waking up early was impossible after night shifts, and she didn't trust the system. She also admitted her money "disappeared too fast" and said she was "trying to quit" gambling.

I felt sick. C was in the other room, laughing, playing, unable to read, unable to tell her age, barely knowing her birthday. Ten years old and completely isolated from the world outside her mother.

I finally said, "So you have a job, access to schools, and your daughter hasn't had any schooling BECAUSE YOU DON'T FEEL LIKE TAKING HER and because your money goes elsewhere?!"

She snapped. Said I was judging her. That I didn't understand single motherhood. That I was acting superior because I don't have kids. She said love mattered more than school, that C was happy, and that reading and writing weren't everything. She told me to mind my own business.

So I told her that C deserved better. That whatever issues F had with her parents, with our family, with the world, her child shouldn’t be paying the price. I said I wasn’t angry because I hated her, but because I remembered the cousin who was raised with care, and I couldn’t reconcile that person with who she is now.

Now things are tense. Some family members think I crossed a line, made a scene, and embarrassed my cousin. My siblings think someone needed to say it.

TL;DR: Reconnected with cousin after 11 years. Found out her 10-year-old can’t read, doesn’t know her age, isn’t in school, and spends days on a tablet while mom gambles. I confronted her and told her she was neglecting her child. Family is split.