She obviously finds Tarvek comforting, and I'm pretty sure uses that exact word in the novel. Gil is exciting, an adventure, but that's a bit scary. Tarvek is comforting, which is plenty seductive in its own way, but might not be as exciting. (A gross over-simplification, I'm sure)

I'm crossing my fingers that Tarvek gets a "you're alive!" kiss when Agatha sees him again, although depending on the circumstances I could definitely imagine plenty of other reactions. It should be interesting and informative.