Would absolutely love to see Sona bringing up this topic herself.
In Indian TV context, self respect gets equated to arrogance. Would love to see Sona having a conversation with Dev about her contract being up and how it's not right for her to continue with the exclusive client in her house while being in a relationship with the Son (her boss). Show her go beyond her 'your mom is my Mom' feeling and be uncomfortable with her employment status. Now that the relationship will be in the open, she doesn't need to be paid to take care of 'her mom' ...
It would be unacceptable to be taunted about this in the near future.
Sona needs to wake up & maturely put the equations right & Dev shown to respect that.