Is field grade article 15 for fraternization normal?

Your friend is getting a slap on the wrist. That PSG is seeing the end of their career and possibly being kicked out a few years shy of retirement. It's very, very difficult to take rank from a SFC, but it's a very simple thing to let QMP evaluate and kick them out.

You only see what's happening to your friend, you most likely won't see what happens to the PSG. Just because you don't see it, doesn't mean that she isn't facing any repercussions from her actions.

Your friend is getting the light end of the deal- if they are still young and have time, they can soldier out of it maybe. The PSG on the other will get an NCOER that makes Trump/Biden look like Angels- no promotion board is going to touch them and QMP will be on them like a steak dinner