Meera "drowned" post leap and is presumed dead but in fact she is not. She is the orphan Gauri. Radha knows about her and I am pretty sure she is the one that saved her from drowning. The police were unable to find Meera in the river, save the torn up dress that Meera was wearing (the police mentioned something about the river being infested with alligators). Ahem and Koki happened to witness Meera's fall into the river. Gopi was holding onto Meera but some slipper rocks made her trip and she lost her grip on her daughter (this was all pre-planned by Radha though as she was trying to get back at Gopi and the Modi family for her husband's death (I believe she thinks Gopi killed him - but I missed part of that track)...
Koki is not at fault for Meera's supposed death but in reality is just missing (no thanks to Radha). She and apparently Ahem as well, blame Gopi for Meera's death which is the reason Gopi hasn't lived in the Modi house for the past 8 years...
The didn't actually show her leaving the house or what happened in the intervening 8 years. We just saw the police bringing by Meera's torn clothing and Koki shouting and blaming Gopi, the next thing we see is Gopi as an art teacher in some boarding school and shortly thereafter Radha (who has been conveniently living in the Modi house for the past 8 years) getting ready to marry Ahem...
Hope that helps...😊