Forgive me if I don't answer the question in its own terms.
Whether it's contempt is for the committee to decide. But in looking to the witness's position, 24 hours later, as you say, the witness learned what she could have said, didn't say, and might have said, perhaps because she didn't know the facts at the time she was before the committee. In any event, she learned what the facts were soon after but didn't say anything for some extended period of time. You have to ask yourself what that piece of information is about, and how important it is to the larger issues before the House.
There can be oversights by witnesses all the time, as you know--myself included, God forbid. After you leave the committee you realize you didn't mention thus and so, and perhaps should have done so. You hope to heck no one noticed or that it was inconsequential. One doesn't come running back to the committee to correct it.