I'm with you OP. One of the hard things is feeling the rage and having to be outwardly calm. Also wanting to tell the world what the fucker did, but needing to not do that to protect DD.
I was hurt by it. Doing that to my child was hurting a part of me too. But my hurt was secondary.
What happened to my DD wasn't rape but she was 6 and it was a her male swimming teacher. Did everything I could but I couldn't get him kicked out of swimming teaching (sly fucker did it under the water with parents around the pool, so who would believe her..?! Also was the funniest, nicest, friendliest teacher. Fucker!).
I found seeing a counsellor helped with the rage purely because I needed someone to offload to who wasn't connected with DD. Then I could be calm outside the sessions and really help DD as well as take the appropriate actions.
I'm glad your DD already has a good relationship with her counsellor and btw the fact you haven't dismissed what she's told you will help massively in her dealing with this. "Easier" than when a parent doesn't want to believe their child.
It's shit that we just can't stop the predatory behaviour of some males and it's our children who pay the price.