I think it depends on the buns in question, but I wouldn't put them together before 2 weeks. This gives her time to heal properly, internally as well as externally.
But as I said it depends on the buns. My bonded pair went back in together after a week, as Autumn didn't bother with her stitches etc and had healed, and charlie is a really laid back bun to begin with, and it was Autumn who was humping him!
Sophie chewed through her stitches three days on, and was not healed( if you get what I mean) three weeks after her initial op, she went for her stitches removed, so she couldn't be bonded when I expected her to be either!
I think it is a case of be sensible, think about the op she has just went through, would you want to be harrased by a randy member of the opposite sex