It's her own opinion though. Sharing it doesn't mean she's forcing it on anybody. Telling the other person that they're stupid and naïve for believing in a higher power, that is forcing her opinion. And it's also what most people mistakenly associate with the "stereotypical" religious person, unfortunately.
And if she's dealing with a possibly schizophrenic individual (which is how I interpreted this piece), then no, religion alone is not going to resolve the situation. And I'm not siding against the other person, because I don't think they were forcing their opinion either.
Could she have handled her own response more appropriately? Absolutely… But you can't just assume that she replied with the specific intention of "shoving her belief down someone's throat".