It's pretty understandable that she couldn't approve publicly so I don't think Isadora would hold that against her, it is her job after all. Betty Burke is Isadora's cousin but they're not on speaking terms (because her mom's marriage to a halfblood) so if Rosalind doesn't mind Isadora ignoring Betty's existence, they could be friendly.
As for the other two, you are right, I don't think they'd ever talk.