Tbh, I never got the impression Nero's mom was important to Vergil personally, the way he reacted to Dante bringing her up seemed to imply that he barely remembed her and was confused about the whole deal. Also he never spared a line or thought on her, even in Vision of V, which explores Vergil's trauma and most defining moments in depth (like Eva's death).
To be honest, I'm glad this is the case too, cause it wouldn't make sense for 3 Vergil to get attached to anyone, since he was all about power and even pushed away Dante, a person he cared about, as a result of it (and partially to protect him, as it was stated that in the end of 3, Vergil didn't want Dante to get stuck into the demonic world, and wanted him to live as a human), he's supposedly didn't spend much time in Fortuna, and given his trauma and the way he views humanity as a weakness, it'd make no sense for him to open up to another human being ever as quickly. It would contradict his character for him to imo.
Also, DMC attempt at romance hasn't be the best so far, so I wouldn't really trust them to pull something like this without damaging Vergil's character tbh.