We read about Yaakov deciding to gather his family and belongings together and leave Lavan's house to go back to his homeland. In 31:19 as they are leaving, the passuk tells us, "ותגנב רחל את התרפים" - and Rachel stole [Lavan's] idols. Eventually Lavan notices they are gone and when he catches up with them this becomes a point of contention resulting in Rachel's untimely demise due to a curse Yaakov placed on her for the theft.
What was Rachel thinking? Did she think she could get away with it? Did she think her father would notice them gone and wave them off?
At least when Avraham messed around with his fathers idols, the midrash tells us that he smashed them all to pieces, so there was nothing to chase after to retrieve, and it helped Avraham concoct a story in his defense. Rachel did not even smash them up. She just took them? Did she think Lavan would not want them back? They were probably expensive so he would not just wave it off! And even if he would not chase them, what good is taking them anyway - Lavan could just go to the idol store and buy new ones?
I think Rachel was making a point. Sure, she knew Lavan would look for them. I think her idea was just to make him pause and think about whether he really needed the idols.
Oftentimes we get into routines and we just continue doing the same thing using the same methods and putting out the same efforts, even if situations have changed. We continue following the same minhagim even if they are not relevant. We continue in the same path we have always followed, just because that is what we are used to doing.
By taking Lavan's idols, she is making him stop and think. Yes, he can chase them down and find them. yes, he can go buy new ones. But all that takes effort. You do not just run off and do those things. He would have to think about whether it was really worth it.
By making Lavan stop and think, she was creating a new situation in which Lavan would be forced out of his routine worship of these idols and re-evaluate whether he really needed and wanted these idols.