My cousin is acting out and having rage fits, what can I do to help her?!

I really need help and advice. Because one of the hardest things is to watch someone you care about struggle and feel like you haven’t done anything to help them.

So My cousin whom is in her mid 20s has started acting out and throwing temper tantrums ever since around the end of last year. I hate to see her act this way as we are really close and used to hang out together a lot and she’s one of my best friends. She now seems depressed and doesn’t really wanna do anything that we used to do before. And I know she has been damaging her relationship with her mom as well. I will be honest ever since she randomly started this having this behavior she has been really unstable and just really hard to deal with. So Long story short out of nowhere she has been continuously bringing up her childhood regarding how it sucked so much and that she will never get over it. And that she just happened to be the “unlucky” one that had her world turned upside down. And that her childhood will always be a “stain” in her life and it’s going to be a lifelong trauma. I don’t want to disclose too much of the personal details and put her business out there but I feel like to paint a clear picture I should at least talk about some of the background. (At least the things/issues that she was telling me)

So basically to keep it simple she resents her step dad lot. And do keep in mind she might sound a little snobby too. But anyways In her mind she used to have a really happy life until her mom remarried when she was little. They moved out of state and life has completely changed for her. Everyone said her stepdad was a really loving and caring person (which he really is) but she disliked him wholeheartedly all because when her mom married him shortly after he was unemployed and completely relied living on disability and government benefits. He had just a little extra income from being the sole caregiver of his elderly parents. In her eyes her step dad was a lazy unmotivated “loser”. She says her childhood ended up being filled with so much financial hardship, embarrassment and just extremely unpleasant memories that resulted from all of that. She also resented her mom for creating this new family. She said she will never consider or accept him as real family because it’s an embarrassment for her and that he doesn’t even come close to any of her real family at all. (Now of course I don’t know the whole story or what the causes is or the reasons for any of that, because it’s not my family, this is just what she’s been sharing with me)

Her mom ended up divorcing her step dad when she turned around 19 (I don’t think it was on bad terms though) and she has started acting out all of a sudden because I guess her mom and step dad still remained good friends after the divorce and occasionally she will borrow money from him which I guess was the trigger point for her. As you can probably tell, she thinks it’s a major shame that her mom is going to her step dad for money. As in her mind he was Someone that stood so low and was a representation and cause for all of her crappy childhood. And she is now incorporating her childhood issues into every little thing that her mom says or does. She will find a way to bring it up and blame it on the past. And this is causing a major relationship damage between the two of them. And I know they love each other a lot.

So without going into any more personal details, I just really need some advice. How can I help my cousin come out of this demonic trance? She is now not functioning right and has been acting nasty and distant at times and when I ask if she wants to get out and hike or shop together, most of the time she is not in the mood. Now I think this is something very important because she also has moved to a new city couple of years ago due to her job and she says she’s been just loathing and hating the city so much, and that her job has been very stressful as well but she’s been dealing with it. I’m not sure if this might’ve been a trigger factor for her crazy behavior but I just need to know what I can do for her. She’s ruining herself and her relationship with her mom, and she knows I am there for her but I feel like this is not enough and it’s not helping. And honestly on a side note I feel like she should’ve not thought and treated her step dad that way despite his financial abilities but I didn’t want to judge her because it’s very obvious that something is bothering her, whatever that is. I’m not sure if this whole childhood thing is just a mask for something else, or if she’s having personal issues but she doesn’t wanna see a therapist because she says her childhood is simply the cause for her depression and there’s nothing that can be changed about her past or her resentment for it.

So Advice is needed please! I feel like I’ve done all I can to be there for her but it’s not working and I don’t know what else I can do to make her feel better. I’ve tried tolerating her little temper tantrums but I don’t think I could continue to do this. And I really wish there’s something else that I can do but I don’t know what or how.
I tried talking to her about all of this advising her to let go of the past, but she said she doesn’t have the “ability” to let go. And that there will always be constant reminders of the crappy and unpleasant memories.
I love my cousin and always enjoy the time we spent together, please share your advices and suggestions!