She is probably feeling threatened with having the other Sevs in the Tank, so that will be why she is eating them.
I would pop Mum and Dad into a Seperate Tank while they are Breeding, let them have the Eggs until they are at the Free Swimming Stage, then pop Mum and Dad into the Main Tank, where they were.
And raise the Fry on your own.
Feed with BBS or Microworms, do lots of small water changes and they should be all good.