The main reason why Tracy recommends this type of schedule is because breastmilk and/or formula should be your baby's main source or nutrition for several more months. Solids are just for practice and experimentation and shouldn't replace nursings yet. In your example, you'd nurse your baby as usual at 7, offer solids 1-1.5 hrs later, and nurse again at 11. This way, your baby has a little bit of an appetite for solids, but you can limit how much you offer so she'll still be hungry for her next nursing. Most babies have tiny tummies, and that's another reason why the feedings are split up like that. Some babies can do both at once with no trouble, and that may well work for you and your LO.
Lots of parents start offering a sippy cup with water at solids mealtimes just for practice, but that's up to you. It's not necessary unless you notice she's getting dehydrated or constipated. Just a sip (maybe an ounce?) is usually enough. And if you keep an eye on her nursing habits, you can ensure she keeps her intake up. If she loses interest or her nursing sessions get shorter, that's often a cue that you might need to limit how much solids you offer. Good luck!