nah she did bed wet even when ma was around, do watch episode 5 at 21:40, sampurna was screaming 'pisi isne firse bistar gila kiya', firse matlab she used to do it frequently but after coming to sasural bon used to think if ma will be with her then she won't get scared n won't do it & yes like you said it could be related with her father's demise even i too was thinking that.
She did then..! Maybe she didn't know that her maa was next to her.. in some epi bon said why aren't you eating food like us and why aren't you sleeping with us ! In that episode you are saying there maa was sitting next to her..not sleeping with her...! Maybe maa was adoring and caring bon because the next day was her marriage day.!
After lockdown epi... Bon says thinking she never bed wetted when she sleeps with maa.!