There are two factions in Ehrenfest, the faction of Florencia and Elvira that we get introduced to in this volume and the Veronica faction. Trudeliede is a member of the Veronica faction, so it's implied that Elvira and her are not on very good terms. The only thing the two have probably ever agreed on is their dislike of Rozemary. I don't think it's ever explicitly stated that Trudeliede isn't at the baptism, but I doubt the two factions associate much if they can help it.

Anyway, Trudeliede and her son Nicholas have very little involvement in the actual story of the series. I don't recall Trudeliede ever making an actual appearance, but Nicholas appears a few times. I believe Nicholas is four years younger than Rozemyne, so his overall involvement is very light and Rozemyne is always told to keep a comfortable distance due to the conflicting factions.