Yes, you can rebond, if they got on well together before then its certainly worth a try. I would bathe them all in the same shampoo (if possible) and then intorduce them all on neutral territory. I find somewhere like the bathroom very good for neutral ground, but anywhere really - even out on the grass. I would make sure they have plenty of food to munch, hay and veg etc and plenty of space to get away from one another. Also no hideys with one enterance (eg iglus) tunnels and bridges are better so piggies can get trapped if being chased.
Put them all in and see how they go, if no fighting has happened in the first 15-20mins then its likely they will get on. If they have lived together before, its likely they will get on again. Sows can be quite noisy and active when sorting out dominance, dont split them up unless any blood has been drawn.
x.
Ps you may also like to try housing the seperate sow in a pen next to the other two for a week or so before bonding.