Ribbit is not fridged, fridging is a very specific literary critique
I need people to understand that fridging is something more specific then just "women dies" if you want to use it as a serious critique. There is criteria to be met here. Here's a good list of thumb.
Do the female characters suffer more in comparison to the male characters, especially in life altering ways?
Is the female character's death not given the same weight as to male deaths?
Do female characters not have a chance to recover from their trauma like male characters do?
Is the death sexualized or otherwise portrayed in a way that seems erotic?
Is it purely in service to another male character or general shock value to the audience?
Could the death be replaced with the destruction of an item belonging to a male character to have the same impact on the character?
Is the character not treated with respect and remembered after death?
Is this the only or one of very few main female character?
Are only female characters dying/not getting revived?
Does she not have personality or purpose beside her suffering/death?
If the answer to most of the above is yes, then it's probably fridging. So let's put Ribbit to the test
While Ribbit does suffer, her breakdown was very important, many other characters go through arcs of suffering, including male ones (or presumed male ones) jax, kinger, and caine, all have a lot of moments of suffering and breaking down. While hers was very visceral due to how seriously it was portrayed in comparison to say, Jax in a maid dress. So I'd say NO, she does not suffer more in comparison.
Her death is treated seriously as a tragedy similar to other abstracted members of the circus. If anything her death is one of the most important tragedies to the story, so NO, her death is in fact given more weight then male deaths like Kaufmo or Scratch.
Ribbit seems to have mostly comes to terms at least on a surface level to being on the circus, similar to other characters. While she doesn't get a chance to recover from the mental anguish of the argument... neither does Jax lmao he's just better at hiding it and it certainly seems to impact Kaufmo as well in ways he doesn't recover from either. So NO she's not signaled out for extra torment.
Her abstraction happens off screen and I certainly wouldn't call the horrifying prickly abstraction blobs they turn into the most traditionally fuckable thing. NO sexualization of her suffering is present.
While her death and how it impacts Jax is very important, her death also has a quite the impact on Ragatha as well and her relationship with Jax and the others in the circus and is not for shock value. However it does have a lot to do with Jax so I'll be generous and say YES her death and how it impacts a seemingly male character is important.
Ribbit's death and who she meant to Jax cannot be replaced by a sexy lamp, her emotional connections and friendship and ties to him are all very important to him. So, NO if Jax simply had his room ransacked, it would not push him into such extremes as her death did.
Ribbit's death is not forgotten, while we don't get to see her funeral because of how we were too late for that, Ragatha makes comments in relation to her, Jax clearly still thinks of her a lot. It wasn't a one arc and then forgotten kind of deal. So NO, she is in fact still treated with respect and emotional weight even long after her death.
The cast is very balanced in gender, With three male main characters, one nonbinary character, and three female ones. If you include all known named in show abstractions, that boosts it up to 5 v 5 (queenie and ribbit) (scratch and kaufmo). So NO, there is in fact a balanced rate of characters and abstractions.
As stated above, the ratio of male to female deaths is incredibly even, and if there was a bias towards which gender is death, and could read it likely would be male due to the expectations of low gender diversity in a programming studio of the 90s. So NO, there's no bias towards female death.
While we don't learn a lot about Ribbit's backstory, we learn a lot about her in the final episode, that she had friends before Jax, that she was exmormon, that she swore a lot before the circus, While she's not super fleshed out, she is very much shown to have her own life outside of Jax. So NO her character and personality is not just Jax.
So as we can see, we get a 1/10 score on the fridging criteria, and even if I'm extra generous and bump up a few i could entertain an argument for (10, 1, 3) that's still only 4/10. She's missing a lot of key elements of fridging.
Female character being dead in a backstory isn't inherently fridging, you can call it out as a cliche, or boring, but fridging is a criticism with genuine meaning dating back to the 90s. You can think it was poor taste or bad execution or think it was a bad direction for the story, but that still does not equal fridging.
You are allowed to kill women in stories, the problem with fridging is when the deaths are treated or handled in a way that becomes very lopsided towards the idea of female characters as disposable in comparison to the male characters. A story where both male and female characters die in similar ways with the same amount of degree of permanency and seriousness in the narrative is by definition not a fridging because they're equally as disposable to the plot and treated the same ways.
Ribbit is not fridged, you can have plenty of complaints about her treatment and the narrative, but it is not fridging. Fridging requires a lack of respect or active contempt for female characters that The Amazing Digital Circus simply does not have. You can wish she got more attention or time, I do too honestly, but there's a difference between a bit underdeveloped and fridged, especially in a cast with so many other prominent female characters who get happy endings.
If I had to give her a trope she's much closer to a Lost Lenore, as a character who is somewhat a love interest who dies before the story starts and then haunts the narrative and has a severe impact on Jax's psyche. It's still not perfect but it's certainly closer then fridging.