How can I emulate a full Android phone on Windows (like a VM), not just apps?

I don’t have an Android phone myself, but my girlfriend does.

I enjoy "tweaking" her phone, so I’d like to experiment on my laptop first and then apply what I learn to her phone later (like patching apps for example).

I’m not looking for something like BlueStacks that only runs apps, I’d like to emulate a full Android system, similar to a virtual machine.

Does anyone know what tools or setup I should look into?