i think you may be partially correct...
i think daadisa indded slapped him because he must have asked Anandi not only for fogiveness but to come back to him - 'Main tumhein Khushiyan dena chahta hun aanandi...Gauri ko chod diya hai maine..laut aao meri zindagi mein" types and there goes the slap...
but as to Anandi not being there...I think they were still shooting the scene and using Anandi's BD for rehersal or something...but in actual shot it will be Anandi only...Mainly because I don't see Bhairon or DS thinking about BDs etc to trick Jagya...