No way she's gonna respond in kind immediately. Hell no. Pretty sure he didn't spill the entire flashback, so he has no resume of his utter devotion. After all, becoming a world-class pastry/cake chef just so a girl you haven't seen in over a decade will say yes at the altar is some pretty wild devotion. It's actually a little frightening? Especially when you combine it with the not having kept in touch?
At the same time, she finally has her little brother back? There is no way she would go down a path that in her mind would inevitably lead to him abandoning her?