guys i don't think radha wants to marry ahem in order to take gopis place, if she wanted to do that then she would have done that a long time ago, i think she only wants to marry ahem so that she can get one over on rashi and knows that if she becomes the elder bahu then she will be given all the responsibities and the keys of the modi mansion which means ordering rashi, don't you remember when rashi insulted her and called her a servant , that is the only reason she is doing that.
radha has never been jealous of seeing gohem together, yeah she had a small crush on him and that's it and she was happy to see how happy her sis and ahem were when she vowed that she will never that rashi cause harm to them after she found out about the swayam thing. Relax :)
besides we are yet to see whether the wedding happens or not.