Don't muddy the waters. You're writing the big reveal scene where a major secret is being told. Unless you're deliberately trying to confuse the reader, don't throw in little bits that confuse the issue. The hero or heroine is learning something about themselves or about their problems and this is a major scene. Why add a mysterious body or the problem another character brings into the mix. If there's a quarrel play it out in full but focus on that alone.
This can be hard to achieve because you want this scene to lead to another and perhaps more important thing. A bit of foreshadowing is all right but to set off on one road and suddenly hop to another can cause a problem. Polish each major scene until it shines and wait to the end to produce the arrow that sends to the next major point in the plot.
Planning is a must here. Not every detail of the story but the major elements from the opening to the resolution are part of a plan or a plot. If your characters want to act in a way different from your plan, stop and listen to what they're saying. This may mean they have come alive or it could be that they're flawed. Remember, a plot is just a plan and plans are always subject to change.