Post leap, Mauli's insecurities are bringing worst out of her. There was a time when Mauli never doubted anything & now she can do nothing but doubt everything & be insecure about it.
Just like how Ross Geller turned after his first divorce with Carol, his own insecurities did damage to him.
Kunal for sure has become better after leap. Probably being a single father with no regrets of past brings that side out of him.
As far as trust is concerned, Mauli's unconscious mind will be able to trust Kunal as far as Mishti is concerned, considering Kunal still remains biological father & it will be somewhere in Mauli's mind that he will not harm her atleast since he himself is a father to Pari & Mishti too is his daughter.
Only grudge Mauli holds against Kunal right now is that he left her alone & Mishti. While she doesn't think much about that as a cheated wife & seems to have accepted KuNan & Pari on some level, as a mother of Mishti, she is hell insecure. Single parents with ugly separation can feel that about their children getting attached to the other.
Mauli is not fighting with Kunal as a cheated wife but as a mother to his child he questioned once. And Kunal isn't fighting with Mauli as an ex-husband but as a father to Mishti for whom he has same emotions as Pari.
As far as Ishaan is concerned, he is the guy suffering in this. He is holding onto a hope, a latch & Mauli is letting him hold on to it for as long as he can. Why is she in splits about Kunal & Ishaan is beyond me? It's her who is not letting go of Kunal's thoughts & bringing him between her & Ishaan.