Oh my gosh. She sounds young, and very, very naive. To say that in an attempt to “convert” you is stretching it. She should have known that it would not be an effective thing to tell you.
However, with that said, I have to agree with Hamlet and jarbaby and others here. So what? So what if she interprets some small thing as an act of God’s kindness? Can’t she interpret these random things any way she wishes? Since you (as an atheist) think this God thing is a bunch of hooey, why be especially amazed that this girl saw this small thing as an act of God? Why is this any more (or less) absurd to you (as an atheist) than the Virgin Birth, or Noah’s Ark? They’re all fiction as far as you are concerned. So why single this episode out as a topic of derision?
Whenever some person tells me such a story, I smile and share in their joy. I mean, for all I know, it’s true. It very likely is true, at least in my belief system, so who am I to decide what can and cannot be an act of God? God is good, after all. So, what is the harm in saying “That’s nice?” and not thinking any more about it? Why do we all have to be so damned smart and clever and judgmental, that we have to be secretly laughing behind other people’s backs about such stuff?
And I’ll add to that. Countless times I have felt like God helped me avoid an accident in bad traffic (I won’t relay the individual episodes here, but a few were a bit surreal). I have many personal tales. I don’t usually share them with skeptics, though, because I understand that they probably would not be fully appreciated. But, I have written about them here, so mock away. Knock yourself out.