Bloopers and Trisna

why do they always use body doubles for trisna when filming with rest of the cast.... they don't even do a good job at hiding it, eg in a scene of parvati and trisna they used a body double of parvati, in all the other scenes Trisnas body double was used!!! is there a problem between parvati and trisna?

It is filmed so badly that no attempt i made at hiding the bloopers, this is totally crazy.