Never, never, NEVER, have a situation in your book, that could be solved if a couple of characters simply sat down for half an hour over a cup of coffee and talked to each other. The Great Big Misunderstanding is a central plot point of many BAD novels, including romance novels, and is guaranteed to drive huge numbers of readers to throw the book against the nearest wall.
You’ve all seen the movies and read the books. They separate when she sees him kissing a beautiful woman. She never asks him why, or anything like that, she just runs away. In the second last chapter someone finally tells her it was his sister and then they all live happily ever after. No, if she can’t manage to ask him why he’s kissing someone she doesn’t deserve to win him. Is her trust and love really too fragile for her to speak to him?
Characters need to show some spine and gumption. If they can’t face facts there needs to be an overwhelming reason why. It should never be just a plot point to keep them apart until it’s time for the reunion and happily ever after.