Is she being neglectful in anyway?

Some babies are chunky, some a tiny. Yes, she is showing that she doesn't care about his health by not listening. At 2 and a half he should be cutting down on the milk and be into more whole food. If you think the baby isn't being properly taken care of, call social services yes it'll be hard but it's better than seeing him be in a place that's not good for him than not doing anything at all.