To answer your question, that specific scenario that you laid out is fine. I mean, it's not unrealistic, and could certainly help move a person from being just a friend into the new category of "dateable".
That being said, you gotta be careful when telling a story about a friend zoned person leaving the friend zone. It could create unrealistic expectations for people IRL because IRL, it's way more complicated. Of course it can and has happened, but one thing I know is that people only tend to put people in the "friend zone" when they aren't attracted to them... Which is why outside of movies and fiction, only "certain" types of people tend to regularly get friend zoned.