Originally posted by: Lord_Voldemort
It wasn't ideal, but it was realistic.
Throughout the movie Shashi is shown to be meek and conservative, she doesn't strike me as someone who throw her husband and kids and start a new life in her 40s. Also, she was kind and forgiving also (it was blasphemous to her that the French guy made advances towards her despite knowing she is married, yet she forgave him and invited him to the wedding. Also another instance where her son spoils the entire batch of laddoos which she painstakingly made - her husband hits the son, but she asks him to stop and doesn't scold her son. All this shows that she is a gentle and loving soul, not vindictive or angry).
Considering this is her personality, of course she would forgive her own daughter and husband. However, she is not the same woman, she knows her self-worth now - she has the intelligence and talent to learn a new language in a few weeks, she also gets validation that she's attractive what with the French guy swooning over her. All this boosts her confidence.
Towards the end both the husband and daughter are shown to be remorseful. However, if they go back to their old ways, I am sure Shashi won't be so meek and will give it back to them, while still not breaking the marriage.