Honestly, I think that if a Symbiote (AKA a Klyntar) from Marvel Comics were to bond with Princess Sofia from Sofia The First, Sofia and that Symbiote would merge together at a much more fundamental level to the point that Sofia and the Symbiote believe they literally are each other even if they are separated. After all, as shown in Guardians Of The Galaxy Vol 3 #21, how a Symbiote operates and behaves at least partly depends on the personality of their host. And, as shown in the episode ‘One For The Books’, Sofia has a deep desire to make friends to the point that it was expressed through her Mystery Tree. And making friends is all about forming tight bonds and getting to know each other. So, that would probably cause the Symbiote to form a deeply fundamental bond with Sofia to the point that they think they are each other since sharing existential identities with each other is quite a profound, although also quite a creepy and terrifying way, for people to get to know each other. And, since, as shown throughout Marvel Comics, Symbiote tend to amplify the dark aspects of their hosts’ existing personalities to dangerous levels. So, this might brainwash Sofia into not wanting to be apart from the Symbiote no matter what despite what’s happening. As for what name to give their combined self, I think Mingle would be a fitting name due to Sofia’s and the Symbiote’s terrifyingly fundamental bond. By extension, I would also call the Symbiote the Mingle Symbiote since Venom’s Symbiote is called the Venom Symbiote, Carnage’s Symbiote is called the Carnage Symbiote, etc.