My coworker is making things awkward at the office

My coworker (F34, lets call her Alex) and I (F28) first met about 6 years ago. Throughout this time we have worked together on and off and have developed a close friendship. We have a lot of overlapping interests and have the same sense of humor, pretty much making eachother laugh so hard we cry pretty much every time we see eachother. She is so supportive, compassionate and caring and I'm so lucky to have her in my life.

In addition to all of these amazing qualities, Alex also exudes Aries energy. She's strong-willed and hard-headed, the type of person to defend her opinions and viewpoints fiercely. She is also easy to anger. When she's flustered or upset, she has a hard time managing her emotions and loses her filter.

For some additional context, we work in a professional setting in the same office. Alex does not like her job. She hates pretty much every aspect of it, but continues on because of the benefits, job security, and decent pay. Recently her inability to manage her anger, coupled with how much she hates her job, has created a situation for me.

Her hatred of the job manifests in her outright saying loudly that she hates her job, this and that, while slamming notebooks on her desk, slamming her mouse around while sighing loudly, and even repeatedly and aggressively slamming her fist on her desk. She often raises her voice and goes on loud tangents about what is making her frustrated. Which is certainly understandable to me, but she does so in front of other coworkers as well as our boss. After these outbursts, the entire office is so awkwardly quiet you could almost cut it with a knife.

Recently the outbursts have become worse. More severe and frequent. So bad that our boss has outright said she should take vacation days for her mental health.

I want to be a supportive friend, but I have always been the type to validate feelings over calling people out over things. But to say that the consistent negativity and walking on eggshells has made for an uncomfortable work environment would be an understatement. Not only for myself but all others in the office. I care about her and want her to make sure she's aware of the impact she's having while prioritizing her mental health, but i know she will be hurt and offended. Plus, she is already aware of her outbursts and has apologized to me multiple times afterwards.

Do you have any advice?