Wow, that’s too bad. Hopefully your SIL will be able to move on from feeling guilty.
I just did a bike safety class at work for one of our safety meetings. I showed a friends helmet after he had a massive crash. The helmet was absolutely shattered but he survived. The accident broke his neck and he had a few other injuries but he’s fine now.
It’s sad that we have to use tragic examples to encourage some safety.
I cringe every time I see someone riding without a helmet. Really, how hard is it to wear the thing? They’re a little uncomfortable but so what? My nephew would be 23 now if he had worn his.