My SIL is still fairly close to my DHs exW. As such she's never really made an effort to get to know me (she's not that close to my DH anyways) however whenever we bump into each other she's always polite. We've invited her for dinner a couple of times but has always cancelled at the very last minute.
I think whenever you're very close to the former in-laws it's absolutely normal to remain that way, but wonder if it changes over time.
I just feel a bit bummed our DS will barely know his auntie (I blame the hormones too!)