This is an interesting Instagram scam.
The account is pumped up to a large number of followers with actual content which I guess is what makes its messages enter my primary inbox. When they send this message, the avatar of the account is changed to the official instagram logo, which makes it look real if you don’t read the username.
I didn’t reply and the next day the avatar has been reverted. The account continues its life as a ghost fan account. I wonder whether I’ll catch it again with its avatar changed.
I reported this chat and account to Instagram as a scam but nothing has happened.