Instead of stealing Lavan's idols (Bereshis 31:19), why didn't she merely destroy them?
As pointed out (in name of Ramban), they were not necessarily idols, so didn't have to be destroyed. This still leaves the question of why would she need them in her possession.
Some sources(eg. 1) note that she might have been waiting for a better chance to get rid of them (throw into the dead sea), since burying them was not a good option (it might cause the land to be more fruitful, thus people would benefit from Avoda Zara), similar to the comments mentioning that there might have been a technical problem with demolishing them.
I recall seeing answers (if someone could verify this with valid sources - גם ברוך יהיה) on a deeper level, that she had wanted to use them for worshiping Hashem. Since this is the method of spirituality she is familiar with she wanted to sanctify it and use it for higher means, rather than destroying it completely. This can be taken further to an abstract level of "being on top" of the idols and controlling them for the good that can come out of them.
Rabbi Kahn, in this lecture notes the possibility that Rachel viewed this item as perhaps having the power to assist in pregnancy/reproduction, perhaps similar to the mandrakes she bartered with Leah for.
The terafim represented that part of Lavan's psyche that he had invested in them. Had Rachel destroyed the terafim she would have destroyed the opportunity to ever again meaningfully communicate with her father.
Because she stole part of his soul she became inexorably bound to him and was unable to exist as Binyamin's mother, remaining Lavan's daughter in her death.
Bechor Shor in his commentary writes:
שהיו מדברים ואומרים על ידי מכשפות ולכך חמדתן רחל
That they [the teraphim] would speak and talk via witchcraft and therefore Rachel desired them.
Thus, Rachel did not destroy the teraphim because the whole reason she stole them was that she wanted them for herself.