That's the defintion for Psychological manipulation, not manipulation such as the physical grooming.

Manipulation is changing other's behavior, especially against their own self-interest.

But if the change in behaviour results in reproductive success, can it really be argued that it is against the being's self-interest?

Yes. It may be good for the species, but very bad for the individual monkey that loses the fight.

Species and individual are human classifications; they have no ultimate biological significance. If I reproduce successfully, then my genes benefit by becoming more common. If I die before reproducing successfully but manage to assist those who are closely related to me in reproduction, I still score a partial victory by having my genes become more common. The only way in which I truly lose is when my whole tribe gets wiped out.

Just by being more common in the short term doesn't mean success in the long term, though.

It's funny to even try and think what success means, given that success only has meaning in the future. I sometimes think of life as a very long proposed logical proof where each step depends on a a step later then it by one tick of the clock. And as time goes by it's continually reduced, a step at time, and eventually we will come to reveal its basis, somewhere out in the future, which is probably is logical false, and will unravel the original proposition, like it never existed in the first place (ie we all die in the end).

Maybe that's all we are, anyway, pieces of a logical computation, which trying to determine something, some solution to a problem that was proposed at the beginning of life on this planet...

Or could the females just be tending to wounds suffered by the most aggressive monkeys?

> Is this really manipulation or is it just sexual selection for bravery/aggression/dominance?

What's the difference?

Sexual selection for traits that otherwise have no discernible survival benefit or even harm survival happens all over the animal kingdom. Selection for bravery/aggression/dominance at least has the potential benefit of defense. Calling this sort of selection 'manipulation' on the part of female monkeys is making an unwarranted and human biased value judgement.

Maybe it's a way to deny them agency and therefore moral responsibility for the results of their actions?

Do monkeys have morals? (Legitimate question.)

Well, they do show in-group preference.

Does that count?

I'd say yes.