"I then asked whether he had insights about where the figure 25 came from, and he said roughly the same thing as Cohen: There’s consensus among neuroscientists that brain development continues into the 20s, but there’s far from any consensus about any specific age that defines the boundary between adolescence and adulthood. “I honestly don’t know why people picked 25,” he said. “It’s a nice-sounding number? It’s divisible by five?”
Kate Mills, a developmental neuroscientist at the University of Oregon, was equally puzzled. “This is funny to me-I don’t know why 25,” Mills said. “We’re still not there with research to really say the brain is mature at 25, because we still don’t have a good indication of what maturity even looks like.”
https://slate.com/technology/2022/11/brain-development-25-year-old-mature-myth.html
Exactly she is an adult who is fully capable of making her own decisions.