Marianne feels that she and her true love must agree on everything.

I could not be happy with a man whose taste did not in every point coincide with my own. He must enter into all my feelings; the same books, the same music must charm us both.

We have evidence that both she and W morph their taste to suit the other -- Marianne as regards Brandon, and W as regards books

Their taste was strikingly alike. The same books, the same passages were idolized by each -- or, if any difference appeared, any objection arose, it lasted no longer than till the force of her arguments and the brightness of her eyes could be displayed. He acquiesced in all her decisions, caught all her enthusiasm, ...

While we don't see W actively change his mind like we do Marianne, he didn't start out liking all the same books and passages as she did. So, it seems to me, they are each leading the other.