It could well be a correct assumption - adolescent males sometimes lack the panache of older roos (bit like humans? ) and can be rough. I'd treat the injury with warm saline solution or iodine and isolate her until there are no signs of blood. Blood send chickens into a pecking frenzy.
I'd separate the cockerel for a while or at least limit his time with the girls. First thing on a morning seems to be "prime time" for mating, so at least keep them separated during the morning hours. To be honest, a few weeks away from the girls will let them recover from their feather loss / injuries, so that may be better.
All the best