Can you get the Feliway diffuser?
It only works in the area of one room, so if they are fighting in several rooms, I'd recommend getting several.
To start, I'd quickly get one 'expensive' one from Petsmart, but you can get them much cheaper on:http://www.petsuppliesdelivered.com/...search=feliway

Can you separate these two with a screen door, so she can see him, and he can get close, yet not get to her?

You can also try putting a drop of vanilla at the base of thier tails. This confuses their scents.

I really think that a slow re-integration of the two would be the best approach, it's a lot of trouble and work, but you can't have Abby injuring herself and getting all wound up over him.

I hope this helps.