People value what they have to work for, and don’t appreciate what comes too easily. This has been proven over and over in many different fields, and applies just as much to the dating world.
So if you don’t ever challenge her, don’t ever question her, don’t ever call her out, then you risk her thinking that you’re the “nice guy” or the platonic friend. She might not even know why she’s not attracted to you—only that she “doesn’t see you that way”—or not anymore, anyway.
Be a bit of a challenge. Most women want a boyfriend who is on their level, not one who puts them on a pedestal.