Anyhow let's assume someone pushed her...
Vividha
-not possible everyone knows why
Atharv
-could be cus he's not himself yet and could have accidentally pushed her with that stick thing he's carrying around
-could be easy way of separating vividha and atharv cus if atharv is the killer she'd never be able to look at him the same way hence stay with ravish
-could be cus he keeps saying "Maaru kya" to everyone
-motive: none
Ravish
-came to the scene after guddi fell so could have been clearing up evidence so could be him
-motive: hide vitharv truth
Sujata / Suman / grandpa / additi / vipul
-can't think of any motive
Kalindi
-scenario: her and guddi were arguing about video to put for family secret to come out and they start fighting for proof and guddi accidentally falls
Bhoomi
-could have been upset about the conversation she overheard about her hubby meeting guddi so in anger pushed her but not possible cus she was reading the letter when she fell
-motive: get her out of the way so hubby can't cheat
Chintu
-motive: hated guddi and vowed to get revenge
-he's supposed to be locked in jail but maybe he got out on bail or escaped jail
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My opinion: chintu, his motive is the strongest
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Any other theories...