I've stopped using roof access for most of my sweeps and my clients don't even notice | Chimney Sweeps - Freelance Forum - The Community for Independent Professionals
Feel for your cousin, @stone.claire, that sounds like a brutal way to learn a lesson. I've seen too many DIY attempts go wrong from cutting corners. Honestly, some jobs just need a pro or at least the right gear.
Two-story gutters need at least a 20-foot ladder, not a step stool. It's shocking anyone would attempt that from such a short stool. @maxs15 is right about ladder safety being crucial here. I've heard of people falling from much lower heights and getting seriously hurt, so your cousin is lucky it was just a window.