Monitoring someone on social media truly depends upon the person whose account is being monitored as it’s his/ her account and they can share whatever they want to. They can choose their audience. They can manage the privacy of their account.
It is always conditional to what extent such information is being passed and used for. And it does not empower the person monitoring it to misuse, blackmail, and morph or to cause any harm mentally or physically.
If there comes any issue of cyber security that person will be punishable under various sections of IT act, which governs online safety and will also be punishable under IPC and POCSO act.