That is correct, but irrelevant to the current case. While there may be no legal requirement to report a crime there is a legal requirement not to lie to police during inquiries into a crime. So specifically, although there may be no requirement for someone speeding to fess up to the police, there is a requirement for them not to lie if their car was caught speeding and the police ask whether they were driving the car at the time.
For the record, I doubt she will get a custodial sentence of a year or more. Most likely a few months, as was the case for Chris Huhne who was sentenced to 8 months.
Well I was replying to LR's general (off topic) post.
On this specific case, I expect Fiona Onasanya will serve a couple of months as you suggest. IMO, based on the press reports, rightly so.
I knew and liked Chris Huhne when he was the MP for my area, but do not think it is is acceptable for someone convicted for attempting to pervert the course of justice to continue as an MP.