My (33m) girlfriend’s ( 30f ) default emotion/reaction is anger, and I’m not sure how to deal with it anymore?

I’ve been dating her for 5 years now, and we’ve lived together for the most part of it.
While the relationship overall is great and she is super sweet and caring, there is also another side to her that pops up from time to time. It’s almost like two different people.
On her better days she is playful, cracking jokes, being overall silly, and even super cute when it comes to animals and plushies. Just a really cute and loving girlfriend. But then the other side just pops up and everything changes. She \*\*hates\*\* working – not just her job, but the concept of working overall, as a society – she feels down because there’s “30 more years of this shit”, and every little inconvenience is exacerbated to high heavens, to which she reacts with, by default, anger.
It can even be just a really small thing, like we’re playing a game that has a particularly difficult level ( and when I say game it can mean those silly casual games like angry birds or something like that ), and she’ll attempt it over and over, getting frustrated, angry and eventually cursing the very existence of the game itself. Since we usually play in turns I’ll offer to take my turn and see if I can beat the level, but she’ll just double down on it – this is recurrent even, if something is not going her way, she’ll just stick with it, even if it makes her feel that much worse and not accept any form of help, and if she eventually completes the thing she’s trying to do it’ll be more of a relief than a sense of accomplishment.
When it comes to work it becomes even more intense. We both work from home, on different rooms because of all the meetings and stuff and so we don’t disturb each other. Right now I can hear her cursing loudly from the other room and being aggressive towards objects. Not throwing them around, but like when you put down something aggressively, semi-slamming it. Almost feels like a bit on purpose, so I hear it and check in on her, which I used to do but right now I’m just pretending I don’t hear it because what follows is a super long rant about life sucking, why do we have to work, how she can’t take another 30 or 40 years of this and we won’t even retire when we get to that age, why do we work 5 days and only rest two, and on and on and on – all things that I’ve tried to ease her mind about in the past, only for them to be repeated a couple of weeks later. I’m worn out and it feels like there’s nothing I can do to make her feel better when she’s like this. Eventually it starts affecting me and my mood goes down as well, at which point she starts being annoyed by it as well, claiming that it’s always like this, and she can’t show emotions because I’ll be down as well, and she’d rather just not talk about anything, “let me be”, etc.
I just don’t know what to do anymore.. I’ve suggested therapy as well but she’s very resistant to that idea. First because she truly believes that it’ll be pointless ( she used to date a therapist even ) and second because she already has so little time that spending another hour or two of her free time per week is just a big no.
Is there anything specific I can do to help with this, or do I just ride it out and accept that this is the person I’m dating? I’m not looking to end things, as it’s often suggested around this sub, but rather to ‘fix’ things and build a better relationship.