Proving Kunal innocent primarily depends more on Siddhi's law n arguing skills than the evidences(they can be secondary),
Witcha already made blunder by accepting that whatever Kunal(his bluff story) is true n everything happened as he said.Now Siddhi can cross examine Witcha with rigorous grilling (she can even put some quick lead questions,witcha will surely commit some blunders) n link her answers with the previous statement,obviously they'll be inconsistent .
She can make use of Section 155(3,4) in The Indian Evidence Act-
3)by proof of former statements inconsistent with any part of his/her evidence which is liable to be contradicted
-Siddhi can prove this by bringing Witcha's past combined with evidences
-Reason for their break up,why she tried to get back to Kunal after 5yrs .
-Her threatening voice mail to Kunal of attempting suicide if he doesn't come n stop her marriage.
-How she left her own marriage n forced Kunal to break his marriage with Siddhi at his wedding venue in front of all guests.
-How she n her dad offered a married man to leave his lawfully wedded wife the very next day after marriage in exchange of Kunal getting his own firm n marrying Witcha.
In all the above what was Kunal's reply to her-We know she never says the truth but again Siddhi should corner her just like how Kunal did n make her speak the truth.
-Witcha acting drunk n making her driver call Kunal(If Kunal really have the intention to molest/rape her then why did he safely drop her home when he has the chance to do so-Witcha being drunk,No one at her house...).The driver n servants can testify how Kunal's behavior towards Witcha was.
-Bringing up Her fake accident n managing to bring the doctor to testify it(otherwise Siddhi can ask How Witcha had engagement party hale n healthy without even traces of any injuries the very next day after having Serious accident -Siddhi can show Medical reports as well as CCTV footage of Witcha's physical condition at the time of engagement)
Why did she need Kunal's shoulder to cry when her engagement was called off,why not her dad or bro.Here Thakral n Rohit can also be cross examined as why was she alone in the hotel room n what was more important for them than being by Witcha's side when her engagement was called off.
For what purpose she went to Siddhi's house the night before the court hearing(Siddhi should show the sms proof n make it clear to Thakral as well as judge that it was not she who went to meet Witcha but the latter called her to meet,if at all Siddhi wanted to plead Witcha to take the case back she herself would have called Witcha but not otherwise)
-Medical examination of Kunal as well as Witcha for any bruises/marks (Now i don't know how much time has elapsed in the show from the engagement day to the next hearing to go with this med examination))
Since Gautam exited the show,Vineet false cases cant be brought in.
This is all what i can think of right now,Sorry if there are any mistakes😳