Yes Devki seems always was seen buckle down in front of Amma but lately she has been very strong.
Once she realised that Dev and Radhika cannot be separated during the ulta phera puja and after that when she witnessed all things automatically done in Radh's favored she was determined to undo whatever wrong was done to Radh.
And when Dev and Radh came back from Bombay and Devki learned that Vish insulted Dev and gave back the mangalsutra.. She was the one who advised Radh to go ahead with her life with Dev and said God is giving her chance to give back everything to Radh which was rightfully hers in the first place and she requested Radh to give her that chance to wash away her sins
She kept on hiding the truth though many oppertunity came to expose it. like during Kshama Vrat and during Dandia night.. She told Radh to conceal it for the sake of her husband's reputation but she was with Radh all the time...
And during all the ceremonies of the wedding whenever some problem came it was Devki's soft and demure voice which got them out of trouble.
Like during Kshama vrat she said we need to fine solution and Shastriji found it in the book
like during phal dan she said to go ahead with the tika and all will be well by God's blessings
So softly but surely she has fought for Radh. Many time she undid Amma's manipulations and stood her ground.
And when Vish ran away on the day of her marriage to teacher she stood with her husband and declared her dead.
She told radh to come our of Vish's mania and concentrate on her own marriage.
Today also Amma tired so much to tell her that Vish was innocent and she was carrying Dev's child and that ONS was not wrong for Vish to ask... though this all was so heavy on her but in the light of the demand of the truth from her husband once again she the weak Devki came up with the truth..
Like previously she was the one who brought the truth of Purab's visit to PB out in front of all and let all know the sacrifice of Radh to cover her sister's missdoings..
She has alwasy obeyed Babuji's direct command every time she was put on the spot. She did not waver from the truth this time also..
It might cost her manythings and that way she will get the forgiveness of her sins but the fact is she told the trtuh is the best thing..