How to make a site mirror in such a situation?

Question

Retargeting

There is an advertising task: to divide the dynamic retargeting campaign of an online store into two - for hot traffic and for cold.
To do this, it is supposed to make a mirror of the site. Site B should have the same theme, images can be pulled from site A, only links from site B should lead to site B.
Site on Wordpress Multisite. Hosting and database for sites are the same.
Questions:
- How to properly link site B to site A's database? Maybe some plugins?
- Links in the WP database for the menu are relative or not?
- Maybe there is a simpler solution for splitting retargeting?