gauri and her reasons to trust shiv
from many days each and everyone is saying that shiv has given her no reason to trust him so much. but after reading your comments and thinking about it I think she has two reasons to trust him there are many more but these two are clear and perfect.
1st reason:respect. since the day they have married shiv wanted her to go away and move on with her life in this process we can say that gauri was hurt but the point is she herself is responsible for this and she is aware of that so we cant blame shiv ( even if what he did to her was wrong ). he never tried to hurt her physically. he had many chances but he never tried to do anything stupid just expressed his anger through words.
2nd reason: friendship after a while a bond of friendship developed and he told her about the potrait. he reavealed it in such a manner that gauri started thinking that the potrait girl was his childhood friend and lover and she is gone from his life and gauri has a chance to win his trust, faith, respect, and love. in this process she did win his trust, faith, and respect because shiv revealed the truth of the kundali to her. the way she cried after the court scene suggested that she cried as a friend who was cheated and also as a lover who lost the battle of winning the love of the man she desired the most. i mentioned friend first because gauri is aware of the fact that shiv loves some one else and she knows that shiv considers her as a friend only and lover because after doing so much for shiv it has no effect on him. ( the line where she says to anupam that she is not angry with ipshita but she is angry with shiv suggested this and made me think).
now we know that the truth he told was half truth but atleast he tried and dared to tell her the truth which jeopardized his life and the chance to have a happy life with ispshita. he did this not once but twice and gauri did the same returning act not once but twice ( hope its not to long and i make my points clear and not repeat the same points and confuse you)