Hi, Warm Greetings!! Myself Rushabh (30) and my wife (29) -- she is an adopted child as her mother passed away while giving birth to her and her sister. They are twins with a minute's gap and her father got married to another woman. Later in 2012, her stepfather died and she was living with her stepmother.
We both come from middle-class families. We being prospects for marriage our families were going through multiple biodatas every week. In this process, we shortlisted each other and decided to meet in person.
Initially, we both met only once where I was impressed with her personality, optimism, communication skills, her matured behaviour, and decision-making skills. Post the first meeting we told our decisions to our families. Then both the families met and they decided the next course of action, i.e., our engagement date.
In July 2021 we got engaged during COVID-induced lockdown.
Considering my job and the distance we lived at, we could only meet on Sundays and used to have 2 to 3 hours long phone calls every night. Either way, she barely spoke to me and made me speak all the time and I told her everything about me.
As she wasn't speaking much, my family thought that she might be an introvert and a bit hesitant to talk so we ignored it.
We got married in November 2021. Now, it has been 2½ months since we got married. For the first 15 - 20 days we didn't bother her and allowed her to get settled in her new life and new home. Then eventually my mom started giving her small chores, which she couldn't perform, which is fine since she has not done any chore before. But now based on her behaviour I think she does not want a change or learn anything new. Honestly, we were not aware of her behaviour with her mom, nor of management skills and, her routine at her maternal home.
Her behaviour is not like any normal girl of her age. She behaves like a child and gets amused by silly and normal things. When the whole family is hanging out together she doesn’t talk at all. When we talk about general things she takes it negatively on herself, she doesn’t even eat properly, nor speak about her likes and dislikes in any aspect with even me.
She never expresses herself in any way and rather takes everything negatively, which has made us more cautious and worried as to what to speak in front of her or what to tell her. So we individually (I, my mom, dad and sister) started to confront her gently and guide her in everything from scratch (like we teach a toddler) but she is not responding at all.

We don't know whether she is doing this intentionally or not. On top of it when she talks to anyone apart from the 4 of us she speaks in a very mature and practical manner that no one can ever second guess her behaviour with us.
Considering our ages, I am afraid that our relationship might be jeopardized because of her behaviour. She had thought multiple times to end her life or to call a meeting with all elders and get separated (she gave me an indirect hint). This is much worrisome for all of us as nobody can cope with the situation in the hand.
I will be able to explain everything in much more detail if we can connect over a phone call or we can meet virtually/in-person.