It’s still a bad idea. If they have some really nasty malware installed it could rootkit your device, and vice versa - and you never really know. Just build a small portable computer (eg. Raspberry pi, NUC, etc) and use their KB/mouse/display.

Other peeps are saying just connect to a remote desktop you have hosted somewhere using your friend’s PC - don’t do that, you can’t trust their software/hardware.