Swasthi, Rashi is a bully and a coward too. They always say that bullies are cowards who take it on those who are weaker than them. If faced with someone like Koki, Rashi does underhand tactics and cannot face her directly.
It was a shock for her with Gopi because of the very fact. The bully in her knew that Gopi was somehow changed and the insecurity was for all to see. She leered at Gopi about being the Jethani. It is not an unknown fact but Gopi is Rashi's Jethani.
In a conservative family like the Modi's the Jethani does hold a bigger command just like Mota Bhabhi does. I am sure that Gopi will not use her position in any unreasonable way. She has always been kind and considerate and very respectful of Rashi as a elder sister.
But now with her won confidence growing and Gopi blooming under the care and affection of her hubby and her maaji, she is seeing the importance of her family which is the Modis. Her need is now aligned to this family.
Rashi is still in RN in her mind and in her heart. She wants to be accepted but she cannot get out of her own world that easily. Partly it is because of her mother and partly it is because she does not want to herself.
Rashi's biggest fear that Gopi will rule over her will never come true but it is also true that Gopi will not be road rolled over anymore. She has become a Modi in her own right.
But I like your last point. Koki has always insisted that both Kinjal and Rashi give Gopi the respect of the elder Modi bahu. For Kinjal she was always Gopi Bhabhi and for Rashi, she was to be her Jethani and not the servant cousin anymore. I hope that Koki does bring in the rule. Rashi needs to stop wanting Gopi at her beck and call. It is two years and the sooner Rashi accepts the fact, the better😊