Meenah’s use of Roxy as a coercive surrogate is a reenactment of her mentor Scratch performing the same trick on Rose with the Tumor. understanding that the Matriorb and the Tumor aren’t just thematic and visual mirrors of each other but in fact serve the very same function in Rose and Roxy’s mirrored arcs, though, we can identify another way in which Meenah becomes a symbolic player in the Lalonde family trauma; Meenah’s also perpetuating a trick that Scratch once pulled on her!
Meenah having rejected motherhood early on in her Beforan life, when Scratch made sure her session was unwinnable and thus forced a reset, he was essentially setting up an elaborate scam ensuring that her quest leads up to this moment where she’s forced to hatch a big troll egg. but where Rose hatching the Tumor was a “suicide mission” intended primarily to ensure her own destruction (with twin Dave coming along as collateral), Meenah sets the bomb off with the aim of ensuring her whole team’s rebirth - setting up her new life post-scratch, she’s forced to symbolically take on the role of mother to all trollkind (a burden which will only be lifted from her millennia later, with her death and the passing of the Tumor-in-Matriorb-form over to Kanaya).
while we can ascribe Meenah’s late arrival to the dream bubbles to the temporal whims of the Furthest Ring, or even to the obscure motivations of the Horrorterrors responsible for them, having made the connection between Tumor and Matriorb it also brings to mind the immense spans of time it can take for troll genes to make their way through the incestuous slurry and finally be born, millennia after their ancestors have died. in fact the chronology of Dave and Rose’s ascension even seems to hint at this same concept in action; while the pair presumably ascend instantaneously on their slabs the moment the bomb goes off, Aradia waits for some time at the pre-existing Sun for them to actually emerge from its surface, still engulfed in the flames that destroyed them. the Green Sun/incestuous slurry is like the Furthest Ring itself - they are mediums without a conventional flow of time, entry into which is not necessarily a reliable indicator of when you’ll get out.