You are right. This whole show makes no sense at all. In the intial flashback sequences, it was shown that both Mohini and Rana (Ram) loved each other very much with Rana promising Mohini that he will always be there for her. Then we see that Rana hated Mohini right from the very beginning and that Mohini was only obsessed over Rana and wanted to usurp the queen's position.
That was intentional. The makers wanted us to sympathise with Mo before they did the reveal. Much like they did in Ek Deewana Tha their previous serial.
In the initial part of the series, we saw Mohini flinch at the thought of hurting Ram even by mistake. Then suddenly, we saw her hurt Ram in various ways. And yes, this Mohini seems very weird. Maybe Mohini took on Gopika's form to avoid being recognized and when the cat is finally out of the bag, Mohini will assume her regular form.
I thought Rehna had quit. On Gopika it looks convincing that she cares for her son. But then i keep reminding that if it was our Mo there’s no way she would care.