

yes, zen4 is the ryzen 7xxx ans onwards. I think they will change the naming scheme again after the 9xxxs now though.
In my case my 5xxx cpu shows avx2 (256bit) in /proc/cpuinfo, I assume you will find avx512 there if you have it.
Also apparently there are mobile and server cpus with 7xxx names that are zen3. It is a mess certainly.
Based on the only information we have, OPs sister is two. So the sister is 2. Trivial.