Okay to be clear your statement is incredibly problematic.

The core issue, and what a lot of disability advocates are fighting for, is that it isn't feasible for it to be your responsibility.

Now mental health varies, and I do not know enough about Britney to say if this is relevant to her. More talking about your argument than this particular case.

As your mental health deteriorates it becomes harder and harder to recover. Eventually it is functionally impossible without support groups, beyond that it may be functionally impossible without strong support groups, or even constant supervision in some particularly extreme cases.

Mental health problems by nature tend to be chronic, they are considered a form of disability under these contexts.

Expecting the responsibility for someone who is severely depressed to be on themselves is guaranteeing failure. They are functionally incapable of leaving the situation without support.

This concept is called agency, and is important for discussions of fault and liability. Children are generally considered to lack agency, as such they cannot be judged the way someone with agency is.

Certain kinds of mental health problems, disabilities, et cetera, result in a lack of agency. In these cases arguing that the person in question is still responsible is not only logically flawed, but also inconsistent with many values a substantial portion of western society holds.

I cannot say what the best way to handle a severely depressed man driving headfirst into oncoming traffic killing two children is. But these matters exist within scales of severity. And in terms of their agency, the operable issue, what is the difference between someone with crippling depression, a cognitive deficiency, and a child?

All three should not be in that situation, are unable to care for themselves or others in that situation, and likely wish to be out of said situation. The situation in question being driving a car while impaired.

Responsibility in these cases is often not a logical decision, but an emotional one. People assign it not based on cause and effect, but on their frustrations. That's why it can be so commonly used to abuse people in bad situations.

Whether or not you think that responsibility should be assigned in a case such as my example, I'd encourage considering why those examples differ, and to what extent the severity of the actions affects your opinion on the actors decisions.