Hmm. I remember an episode where they joked about her being older. I’d have to revisit it, but found this upon also googling.
https://dorksideoftheforce.com/2021/...the-bad-batch/
“While we don’t know Omega’s exact age in numbers yet, it was implied in episode 15 — and confirmed in episode 16 — that she is older than the other members of the Bad Batch. She was already old enough to remember them being experimented on in Nala Se’s private lab before leaving her alone again.”