There's a lot of variables in play bruv, but you need to think about it in terms of a network and not just location.
To get to Valorant servers, you need to get from:
your computer -> your gateway in your home -> infrastructure back to your ISP -> out their core infrastructure to the rest of the internet -> get to the ISP of the Riot servers (in the datacenter where the servers are), then to the Valorant server itself (and back to you).
If you want to know exactly where you're gaining latency, you would both want to run traceroutes to the server and see which hops are taking longer for you (and which different hops you take than he does)
Server IPs for traceroutes are here, but article is a little old so I cant really confirm how valid it is now:
https://support-valorant.riotgames.com/hc/en-us/articles/360047225674-How-to-Use-Tracert-to-Obtain-Network-Logs
If anyone wants to ego check me on this, I welcome it btw