The sidekickless Colbert Report was my favorite show for 9 years. I don't need a sidekick to enjoy a late night talk show, and I'm sure I'm not alone. But you bring together a focus group or two, which I have absolutely no doubt that CBS has done, and you'll get a chunk of the public who is not only accustomed to a sidekick, but think something is missing when there isn't one.
Batiste was hired as band leader and sidekick (in kind of a Max Weinberg role), but, after gradually finding out that he has trouble stringing words together- at least on camera, Stephen has been looking for someone else. Meredith is the new sidekick. They've attempted to introduce her as organically as possible ("hey, who's over there? It's Meredith! Hey Meredith, how's it going?"), but for any non casual viewer, the smoke and mirrors are an obvious attempt to hide both Batiste's failure to fulfill this role and their failure at putting their trust in him.
Compared to Batiste, she's great, but that's not saying much. It's still very early. If memory serves me correctly, she's been on camera about 5 times, but 2 of those were the stuffed animal prop holding gags where she said practically nothing.
I'd give her a chance to settle into the role. If, after a while, focus groups find her annoying, expect to see someone else gradually introduced.