Hi everyone, hope everyone is doing well. I apologise for the long post but I would really really appreciate anything.
I'm going to ask for advice/information in regards to my sister.
My sister is 32 and unfortunately has not had an easy life in terms of self-esteem and confidence. Looking back, I think she has had depression since early 20's but she has never been too bad. As children, we were rarely allowed to go out and socialise (daytime was fine but not night time) so as we got older, we missed out on a lot of socialising (and in turn being confident with other people). My parents used to argue sometimes and for some reason this has really affected my sister, and whenever they would start to argue she would have panic attacks. When she got married, everything was fine but things with her in-laws became really bad and they really made her life difficult and her husband never stood up for her or acknowledged what his parents were like towards her. About a year into the marriage, they moved out and his parents were never happy with it and from then they rarely spoke to her and really made her feel bad. They are now divorced but even though they had a lot of problems, it came as a shock as my sister and husband talked about things and he said he would go and talk to his parents but they next day, he took all his things and left. He has always been a weak person when it came to his parents, as they rely on him a lot and he was never able to stand up to them. Anyway, as the divorce was going on my sister has a few moments where she was really really stressed and something happened to her. She would be sitting there and almost become child-like and not really understand what was going on and be really confused. I personally think it was her body's way of helping her cope - a coping mechanism (I think regression). After a few mins, it is like she just realised everything that had happened and would be sobbing uncontrollably and be so scared, almost like a panic attack. At that time she kept screaming and tried to take her wedding ring off and was just inconsolable. Then it would be like her energy just went and she would just slump.
While the divorce was going on, she stayed in the marital home while the husband went back to his parents. She seemed to be fine having her own place and she dealt with things well and joined yoga classes etc and actually developed a social life. It's been a year since the divorce started and she has now had to move back in with our parents (since the marital home was under the husbands name). And since then I think she has become worse, because to me it is like how when we were younger. My parents really worry about her because her moods are up and down but I feel she has a lot of anger towards my parents because of how they were when we were younger. Even though she in 32, she gets annoyed that she has to tell them where she is or gets worried if she wants to go out because then she will think my dad won't like it and then shout at my mum. A few days ago, I went over to my parents house and straight away I could tell she had been stressed all day. Later on she came in to a room where I was changing my sons nappy and I asked her if she was ok and she said she really wanted to go out with her friends and maybe stay the night and was dreading telling our parents. I felt like she just needed to get away so I later said to my mum that she is wanting to go and to just let her and not say anything (not that my mum says anything, but she'll want to know where/what time she'll be back) and my mum said thats fine so I went back to my sisters room and said that our mum was fine and she just said 'really?...I'm so confused' and she changed again and kinda zoned out. I said to her 'you are stressing out about this so much that it's getting to you, they said it's fine' and she just said 'whats wrong with me, have I got a mental illness'. And I said to her that we need to get her to talk to someone to figure out what it is that happens to her so we can understand and work to making her feel better. This time she zoned out and then back in and then said 'I'm feeling better now'...and I asked her to tell me what she feels when it's happening and she said it's like a dream but it's hard to explain. I personally believe there is something that she is battling. She used to be on medication for depression but stopped. At the moment she isn't really talking to anyone, I message her but don't hound her as that might make her push me away. My mum is really struggling with her and she is just scared for her, and she messages me each time my sister is not talking to them and always asks me to see whats wrong. I think having her own place would help a lot but financially it's difficult
At the moment, I am trying to:
-Find something to help my sister, maybe CBT
- Try and get my parents to back off a bit.
- Get my sister to communicate a bit more
- My grandmother (mum's mum) had a stroke back in december and is fully dependent on family (can't walk) so my mother is stressed with her and also my sister. So I'm trying to help with my sister so my mum has one less thing to worry about. My mother is in her 60's so I don't want anything to happen to her with all the stress.

I can't stop my parents for worrying - i think they are scared at this time that when she goes out she is vulnerable to other people because of the divorce and generally because she is kind of fragile minded. She overthinks and gets cautious and anxious over things.

So I think that's it, my main thoughts are regression and depersonalization but I'm not entirely sure if they define this situation or if they play a small part. Also, we were never abused as children, although our dad used to blame our mum for things and we were always worried to do things in case he shouted at our mum. E.g - our brother always used to go out and my dad didn't like it but would always blame our mum. So I suppose we were affected emotionally but my me, my brother and other sister are ok but this sister seems to have kept all that with her which she is aware of and asks why she is messed up.

Thank you for reading, I honestly appreciate any help.