Haha, well, I'm certainly not endorsing either. Let me try again. If the LW's suspicions are wrong, further investigation may result in hurt feelings and exposing an ugly part of the LW. The LW has to risk it, though, because if the LW's suspicions are correct, the consequences of failing to investigate are much worse.

The comment about power was just to say that I can understand why, after seeing something suspicious, the LW might recall what his/her sister said about control and attribute new significance to it.