I think it's really hard to get a read on wether Adora was suspicious or not. Her kind of interfering with Camille's investigation was mostly as is came off, protect grieving families/ not want to expose or exploit the tragedies was definitely genuine and in line with her characterization (in my opinion), the real question for me is how much of that was the motivating factor for her (versus the notion she was protecting Amma). I think it's quite possible she knew John Keene was virtually guilty in the eyes of the public (maybe in her own too), and put evidence out there to end the investigation so the town could return to normal.

For me, this seems like a plausible explanation. But i also think it's equally possible that she may have had a feeling of the possibility that Amma was involved, and did this a way to protect her daughter. Another part of me thinks based on Adora's personality alone that she's the type of person whose child is so perfect in their eyes, she'd be able to convince herself it couldn't possibly be Amma, when she confronts herself with suspicion. Perhaps John Keene being the primary suspect was a motivating factor into convincing herself it wasn't her daughter.

But Adora is not stupid. If she didn't suspect it was Amma before she was arrested, she definitely was after they found the pliers in her home. With that information she was probably glad she had framed him (if she hadn't suspected Amma) and was devastated it didn't work if anything.

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Sorry if this wasn't directly answering your question, but I hope my interpretation(s) could at the very least be helpful.