I am also a firm believer of the fact that Devki will not openly support Radhika.
Dev has to remember the various dialogues he had with people and put 2 and 2 together. As recently as when Dev and Radhika were leaving for Malaysia Devki had that conversation with Dev where she tells him that Radhika deserves all the happiness for having sacrificed her happiness for others. Dev did have a reflective look on his face. Please Dev it is important for you to remember these instances.
Lots of truths have to tumble out, the burning fiasco, the attempted bridal swap which even Vaishali and Mrinalini are aware off, the burning bangles incident which Dev is aware off and the ability of Radhika to swallow all these without any retort will all start tumbling out.
Vishaka herself will be the saboot for the first marriage truth. When all her attempts have failed she will accept her folly and in the bargain will be the saboot. The reason is she kept saying saboot, kanoon aur samaj mere saath hai. She will lose this one by one. God give Radhika strength to stand tall and face the effects of the truth.