The reason i don't hold it against Radhika..
1) She must be grateful to her parents. No matter how selfish Devki has been with regard to Rads and Vish, and no matter how helpless Shashtri has been in front of the society or Amma when it comes to treating Rads as an equal, they still have bred her for years. If not for their support Rads would definitely be in a deplorable condition. They've provided her with home, food, clothes and love even if they've given more love to their own daughter (arguably) they've still given Rads a part of something she didn't have any rights on by birth.
2) No matter what she does to gain for herself the rights of being Dev's wife, it will now be seen as she stole it from Vish. Amma's cursings have little meaning to us, but in Radhika's own eyes she cannot steal her sister's happiness. So she herself cannot be the cause by which Vish is kicked out of Dev's life. If it happens that way then Amma will be proven right, which is just going to be tragic. Rads will come out looking like a husband stealer... which is just not what i want to see.
Instead the truth must come out in a way where no one can point a finger at Rads. And i feel that Radhika's Kanha also wants the same. Thats is the reason whatever happens is happening because Amma herself is puttiing Rads in those situations. Amma put Rads in the mandap and now asked her to perform the pooja too. Rads cannot be faulted for that...tho Amma will still blame Rad's evil eye.. but no onlooker can say Rads did something to gain any such rights. So Rads will not speak.. she won't say anything and only another circumstance will bring out the truth for everyone. Thats just the way its got to happen.