Hi Rakesh! Welcome back to TeenHelp! I hope you find the support you are looking for.
I am going to be completely honest and say I know very little about Indian culture, and so my response may not be the right thing or even a possibility, but I will try and understand.
It sounds like your mother may indeed be suffering from some sort of illness, possibly psychiatric or maybe a physical illness that just happens to affect thinking processes and moods. It also sounds like your wife may have some trauma, or even PTSD (Post Traumatic Stress Disorder) from the way she was treated in her childhood. Only a doctor can provide official diagnoses (and I am definitely not a doctor) but those things both sound like possibilities.
Honestly I would suggest fostering openness and honesty between you and your wife. You say she doesn't always talk about the situation but you can tell what's wrong. Maybe you can broach the subject with her? Marriage is a strong bond. You made a promise to support each other for the rest of your lives. Furthermore, you have a child together, which is an even stronger bond. She needs to know that she can trust you and talk to you.
I don't know what the stance is on therapy where you live, but no one can be someone's everything. It sounds like your wife may really benefit from talking to a therapist or other professional skilled in seeing clients with mental health issues, especially trauma. I know this might not be possible for many reasons, but if it is possible and it's something she thinks she's comfortable with I think it might help. Your wife could also possible try to find a support group to meet and talk with others who have been in similar situations. Those are generally low-cost and sometimes even free, if finances are an issue for you.
As for your mother, is it possible to get her to a doctor? It sounds like she might be able to benefit from some kind of medication, whether it's for dementia or mental health stuff. I realize that might not be possible, but between your wife accessing resources for trauma survivors/depression and some medical help for you mother you might be able to remedy the situation and everyone can get to a better place.
I hope this helps at least a little. Good luck, and
PM me if you need anything.