I think they should totally be friendly, yes! Partly because of close proximity and partly because, yes, Margaery and Brienne pbs being friends is too good to pass up. And yes to notes :)
Not likely much for Vathra with Sylvaine, but my next-in-the-works might have some interaction available!
Sylvaine probably is at least acquainted with Luren, and has probably managed to briefly compliment his craftsmanship (she doesn't stutter as badly when "talking shop" about weapons/armor/fighting, or when reciting the Chant).