Your are very right, it's not healthy for the budgies to be kept in such conditions and in a state of constant stress.
The whole flock is at risk of suffering physical and mental damage and the same goes for the aggressive male budgie who by now must have deep rooted mental issues.
The only way to work with a pet bird who has severe behavioural problems related to aggression is by isolating this bird from the flock and to have one-on-one intensive training sessions with the goal of having this budgie to bond with the owner and to use positive reinforcement skills to hopefully rehabilitate the bird or at least to diminish the aggression.
Even if training goes well, this doesn't mean the bird will necessarily be able to live in a bigger flock environment and in this case common sense should be applied and a permanent decision should be made in terms of providing long term harmony and happiness within the flock and this problematic budgie who clearly doesn't do well when housed with multiple birds.
The best thing you can do for your friend in order to avoid future heartache and taking in account all pet birds involved is to have a serious talk with her, and to try to discourage her from keeping pet birds and breeding them.
RIP sweet Tito (Summer 2008 - January 17th 2013).
You are missed and never will be forgotten.