To be fair, Lupa isn't quite the vacuum of charisma that MarzGurl is, and I still maintain that MarzGurl has somehow proven herself over the past year to be a level of crazy that even Lupa can't reach (because her arms aren't as long).
I think the root of Allison's problem, more than anything, is simply her chosen media of specialty. While the core audience of TGWTG may have had a healthy percentage of weebs, one could also make the case that Kaylyn tapped into a different sort of niche not a lot of other people could cover with her anime reviews, as droning and nondescript as they were. Allison, meanwhile, is just another film reviewer. The site had already been oversaturated with those guys even by the time she joined it. At that point for her it became a question of "Okay, so you review movies. Literally everyone here has reviewed movies to some degree and a lot of them specialize in reviewing movies like you do, so what do you bring to the table? What do you have that others like the Nostalgia Critic and the Cinema Snob don't?" And unfortunately (for Allison, not so much for us), she just couldn't keep up with the rest of the crowd.
So Lupa needed assistance to get by in the surprisingly cutthroat industry of Internet content creation, even with the smaller round of competition that TGWTG provided for her. She couldn't quite do it alone. So what she did for more exposure was collaborate with some of the bigger names of the site. If it weren't for her long, well-documented history of Internet shitfits, you probably wouldn't have known who the fuck she was if she didn't make a guest appearance in Doug's review of The Room. But since most of those bridges have long been incinerated (all because of her) and the only people willing to touch her now are those in her bitchy little in-clique, her content has been left to suffer and she gets left in the dust as just another shitty YouTuber.