Louise not only burned any bridges but cut away the banks of the river.
According to Susan, this is not true. I don't think Susan has anything to gain from actively shunning Louise, even though she has been wronged. If she wants a relationship with her brother, it is in her best interest to take the high road.
That's my feeling on this. Yes, Susan could totally trash Louise's reputation in the family with only a few words, all of them true and even polite. But what would she gain from doing so? Louise wouldn't "get away with" her ill-thought-out stunt, no, but there'd be no hope for reconciliation, and it would affect her relationship
with her brother. By taking the high road, she's leaving the door open. Hopefully, Louise has learned from this incident, and they can build on that.