Here’s my take on this. You’re right, Instagram is designed to keep DMs and a lot of activity private, so there aren’t many direct ‘signs’ visible to others.
On one hand, you can look for patterns in public activity. Frequent comments, tags in photos, or consistent story interactions might suggest a close connection. However, this is largely guesswork and doesn’t tell you anything about private messages, which is where most conversations happen.
On the other hand, a more direct approach involves using monitoring tools. Software designed for this purpose can access the app’s data directly on the device, showing you the actual DM conversations and shared media. This removes the speculation, giving you a clear view of their interactions instead of just public clues.