Welcome to the SR family!
Please make yourself at home by reading and posting as much as needed. I find lots of wisdom in the permanent (sticky) posts at the top of this forum. Some of our stories are also posted there.
Based on the information in your post, it appears the ex gf is taking on responsibility for your friends recovery. That the job of his sponsor. Hopefully, he will find his way through this added attention with the help of his sponsor.
Not much you can do otherwise. You did not cause it. You can not control it. You will not cure it.
Vent away if needed.
How are you doing in taking care of your needs during this transition?