This may be ugly truth to tell, but you shouldn't put Mel through more trauma just to feel you didn't do her harm.
Shoving her back in, while still handaling trauma, is nothing but avoiding responsibility. Saying "She's okay, she didn't see a man dying, and he wasn't on our side anyway" when she's still having flashbacks and nightmares, is belittling what she went through so you can feel okay with yourself.
It's not okay to deprive your friends of support so you can feel you did nothing wrong. You can feel you did the right thing and still support a friend, who is going through a hard time.

There's always a price to pay.