You're right that we are never told outright how Caroline Bingley feels about Darcy. It's obvious that for her, marriage is first and foremost a business decision, and that Darcy would be a great catch. However, we are told that, in a world where young women were always making compromises to ensure an eligible meal-ticket, Darcy also has many personal qualities that would make living with him a not-unpleasant thing: health, looks, height(!), intelligence, wit, knowing how to behave in public (most of the time), etc. I doubt she loves him, but IMO, Caroline Bingley is quite looking forward to being Mrs. Darcy, and not just from a practical POV.