Telling your neighbor that she's "out of order" for calling social services on the other neighbor may not be the most constructive approach. It's essential to approach such sensitive matters with empathy and understanding for both parties involved.
Leaving a 12-year-old child home alone for an extended period, especially until 6 pm, can be a matter of concern from a child safety perspective. Laws and guidelines regarding the age at which children can be left unsupervised vary depending on the country and region, but 12 years old is often considered young for extended periods of unsupervised time.
Rather than criticizing your neighbor's actions outright, try having an open and non-confrontational conversation. Express your concern for the child's well-being and discuss the situation calmly. Encourage her to talk to the neighbor she reported or consider having a conversation with the other neighbor yourself to understand their perspective and the arrangements they have in place for the child's care.
If you genuinely believe there's no immediate danger to the child, you can also suggest alternative solutions, such as helping the family find suitable after-school programs or childcare options.
Ultimately, everyone's intention should be the child's safety and well-being. Engaging in an open and understanding dialogue can be more productive than passing judgment or criticizing each other's actions. If you're unsure about how to approach the situation, you can also seek advice from a trusted authority or organization that deals with child welfare in your area.