You are comparing story of Anandi's deeds with a character that has been around for just 5 months? Anandi's been shown for 5 years! How can you compare their deeds?
Also with what torture that Ganga used to face she is not expected to do things for all. She was timid even to speak to Singhs. For God's sake! It's a woman who twice escaped attempts to murder her!! And got burnt, beaten and sexually abused since childhood!
Anandi's faced way less suffering than her. So she can bond with others ans think of others comparatively more.
Ganga has begun to open up only since a month or more. She was a girl whose mouth used to be tied up if she uttered a word.
Ganga did not suspect Kanchan or react on spur of the moment. She is realistic. She has had firsthand experienced of the worst face of humanity since childhood. She is practical and rightfully exercises caution. She is cautious not merely suspicious. She spoke about Kanchan to Singhs only after overhearing her father's conversation with the lawyer. Otherwise she was fine but merely asked Jagya to be alert.
It's not like she can't see goodness. For a person who has seen the worst side of the world since childhood and practically experienced it she is realistic.
Shiv is also intuitive and exercises caution around people whose conduct generates something is amiss. It does not mean he can't see goodness in others or is any way less.
Sorry but for whatever Anandi has faced she has lived a pretty sheltered existence compared to Ganga who was exposed to brazen torture and abuse since childhood. Witnessing suffering or social evils is different from actually experiencing every possible abuse.