You shouldn't need to cold set the frame for only a 5mm spread. The hub won't slide right in but it will go. I've put 130mm hubs in 126mm aluminum frames without major issue, though it's slightly more effort than doing the same with a steel frame.

As to alignment issues. your disc brake caliper should have plenty of adjustment to handle the very slight angle the disc brake tab will now be at.

Just curious though, what hub did you have in there originally? I didn't realize any frames were made with 130mm rear spacing and disc brake mounts since I've never seen a 130mm disc hub. Are you sure it's not an in between frame like Hillrider has suggested or a 135mm frame that is out of alignment?