You can just rub the ribs with oil, then apply the rub. I have done it many times, and the rub sticks fine. I only use mustard on butts, and you can use oil on those too. And the oil brings out the flavors in some of the spices.
I don't see any reason Adobo wouldn't taste great on ribs. Adobo can vary in the combination of spices, but basically it is sweet paprika, black pepper, onion powder, dried oregano, ground cumin, chipotle chile powder, and garlic powder. All of which are commonly used in pork rubs. In fact, I make my own rub, and it uses all of those, except I use Ancho chile powder instead of the chipotle.
If she likes a sweet tasting sauce, you might want to try "Bone Suckin Sauce". If it's too sweet for her straight up, you can always mix in a little vinegar, or add a little of some other sauce. I personally use it to mix with other sauces to balance everything out. It doesn't have any smoke flavor, which I appreciate. I'm not a big fan of using a lot sauce. Only as a "condiment" and never on brisket, just a light coating on ribs, and very little, or none on pulled pork. And I don't really understand why anyone would want to use a sauce with smoke flavor added (or add liquid smoke to their homemade recipe). I want to taste the smoke/wood choice from my SI. It's hard to find store-bought sauces without smoke flavor.