It's highly possible.
It's likely what was happened.
At first I thought it might be BO's work, because they misinterpreted Ayumi as Haibara since she wore the same clothes as Haibara used in that video. But BO wouldn't do something recklessly like mistaking someone (Actually they ever did it when mistaking Sonoko as Sherry in Movie 5). However, even Ayumi's hair was hooded, her uncovered black hair bangs couldn't be mistaken since Haibara has a brown one. Also, if they were really BO, they're already gone too far for figuring out that Haibara was a shrunken Sherry only with a single look, not to mention they saw her only from the reflection (However, it can be possible since BO isn't an amateur organization, but still-).
Something I have in mind is, Haibara's reflection can't be seen without zooming it. Nah, normally if we're only about to watch video online, we won't notice that vague reflection on the glasses unless we look for certain something there. As for Sera, she noticed it because her detective instinct suddenly worked when noticing something weird, not to mention she maybe has known Haibara Ai long before (From Akai Shuuichi for example if she's really Akai's sister). So far, it's really interesting case. I can't wait for the next update.