I think Bani sacrificed a lot and provided Pia everything that she needed. When she was young, the needs were small, but as she grew, her needs also increased and the desire to have it also increased. The condition of her father might have also affected her thinking and probably she felt, if at all they had lots of money, they wouldn't have gone through all these troubles or may be she could have got what she wanted. Moreover, her father was most of the time drunk and love between sisters might have dissolved any shortcomings and so there was no opposition or cross arguments among the members of the family. And when they entered Walia house, the richness coupled with the taunts, the inability to produce the money to save Rano or Mt.Abu house without going through the trouble might all have been forced her to think that money is everything. And coupled with this, the opposition that she faced by Seema and her husband for small requests like food that she liked (which she easily got from Bani) hurt her ego. Unable to adjust to the extreme and unable to compromise the desire or with the circumstances, unable to communicate properly with the family members including Pushkar, and also a remote guilt of having running away pushing Bani into unwanted marriage might have all made her the way she is today. I may be wrong, but this is just my way of seeing at her behavior.
In a way, it is good that she has come to bani crying. Now, Jai will know how lucky he is to miss Pia in his life as a life partner. Also, she will put up a fight with Rosh (equal strength), which will engage the two (pia and Rosh) to outsmart one another and so, their attention will be diverted from J&B, and the two will get time and attention for each other leading to a strong bond. Jai can now compare his 2 X simultaneously with Bani. Bani will be DIAMOND FOREVER and Rosh and Pia will be like glass pieces. Moreover, Jai had blamed that Bani had planned all these through her sisters to get into Walia household (the night the sisters left Walia mansion episode). Now that Pia has revealed that, Bani was not interested in marrying Jai and was forced bcos she eloped, the tubelight will light up to see everything clearly and so, the accusation regarding the money will also be cleared. Ranveer's plan will flop!
Isn't that good!