The scattered peepers on the ground can be performed at any time. The point is to familiarize the chickens to them so when they see them on Meredith, they won't think them as alien. But make sure they are still on the ground when Meredith makes her grand entrance.
As for the water issue, as long as the nipple is above her head, Mer shouldn't have trouble seeing it. The peepers block vision straight ahead, but allow for overhead and things on the ground. I really don't think she'll have a problem.
No need for Meredith to have additional confinement after getting the peepers. In fact, the distraction of reuniting with the flock will take her tiny mind off the peepers.
At first, right after Mer gets the peepers installed, she will only see them, not anything else. After about ten to thirty minutes, she will begin seeing other things, and the peepers won't be in focus any longer. It's usually a very quick adjustment.
As you install the peepers, you may notice her comb will be squished. Just fold her comb over and don't worry about it. It won't bother her. The prongs are spread open with the snap ring pliers (they work the opposite of regular pliers) and you slip them into her beak holes. It may take a couple tries to get them on. It helps if you wrap her up tightly in a towel and cover her eyes. Having someone hold her would be a big help, but I do it just fine by myself. This doesn't hurt the chicken, though it's uncomfortable at the very first.
You should see a dramatic difference in the way she relates to the rest of the flock since she will have trouble seeing them. But there are no guarantees that she won't relearn to be a bully after wearing the peepers for a few weeks. My four Sussex, all four sporting peepers, intimidate all the rest of the chickens in spite of the peepers. The whole flock is afraid of them, though the damage they inflict is minimal since they still have hampered vision.