Vanilla Hosting

Hi , we have a already existing e commerce site like "XYZ.com", now we have created a forum for this let suppose "abc.com".we want to access this forum with "XYZ.com/vanilla-forum". What is the best possible way to achieve this? One approach we are currently using is we are creating a reverse proxy for this for all assets like css, js whereever we found "vanilla-forum" in url we migrate this request to "abc.com" like "https;//abc.com/vanilla-forum/design/custom.css". Is this the right way or we can also achieve this by nginx configuration?