1. she was the one who provoked ishita to know about pallavi-pragati truth
2. she inculcated in ishita's mind that pallavi might be killed by chadda on the day of chadda's murder because of which ishita went to chadda's house
3. she gave that poisoned water to ishita when sarika mixed poison in water tank
4. shagun-abhishek-shanaya(ishita) encounter at the hospital(she accidently informed abhishek😕)
most probably she'll be the one who will be involved in disappearance of ruhi and blackmailing ishita to do something(don't know what but something big according to promo) that will ultimately lead to ishra separation
shagun must have launched niddhi to use her in taking her revenge over bhalla family