I’ve dealt with something similar, and it usually comes down to jealousy and routine changes rather than the other dog being “scary.” When a new relationship shifts your attention, some dogs start acting out for reassurance. What helped me was setting clear boundaries, keeping calm introductions, and rewarding relaxed behavior instead of reacting to the barking. Slow, neutral-space meetings between the dogs also made a big difference over time. If you’re looking for more structured tips, there are some good training guides you can find through a quick link that explain gradual desensitization and multi-dog dynamics in more detail.