It’s understandable to want peace of mind, but “quietly logging into her Instagram without her knowing” is ethically messy and can cross legal lines depending on where you live—plus it risks breaking trust in a way that backfires with teens. A better approach is using transparent parental controls/monitoring (or at least a boundary-based “we’ll review together” plan) that lets you review activity and block risky content.
If you want actual phone monitoring that’s built for parents (not stealth login), mSpy is one of the common options—typically used for monitoring messages, apps, web activity, and setting content limits from the parent side. TL;DR: avoid secret logins; use a parent monitoring app like mSpy for safer, kid-targeted oversight and controls.