What's the problem with stepping on toes? If you do, the worst that could happen is your mate gets the hump for a bit. If you don't and there's something really wrong, well......
Not digging you out specifically here. I would have been of the same mind in the past but if someone is genuinely having a really hard time of it, my experience is that if you push past the initial block, then people can open up. Sometimes you need to persist and give them permission.
I know it's not that straightforward and none of us are trained experts in wonky brains but sometimes it's worth considering having uncomfortable conversations.