Now I don't necessarily agree with some of the lockdown rules or the enforcement thereof but in this case I have sympathy whatsoever. In my mind a huge difference exists between conduct when you potentially could be asymptomatically spreading the virus (i.e. what most of the health protection regulations are meant to prevent) and doing something knowing you are infected with the virus for your own convenience which is what happened here. Travelling on public transport whilst knowing you have a positive test is not a potential risk of spreading the virus it is a defined one.
My knowledge of Scottish law is very limited, essentially that common law offences are used far more, but reading the applicable Scottish laws (
Coronavirus (Scotland) Act 2020) and the various regulations I don't see a statute she could be charged under and there have been convictions for knowingly exposing others to a risk of infection from other viruses under the common law offence charged. Generally Scottish common law charges are far more common but the laws themselves are defined by previous court cases so the procurator fiscal (who decides on the charges not the police) can't just magic a charge out of thin air.
A lot of Scottish offences have rather grand and huffy-sounding names.
Including my favourite obscure but still chargeable common law offence
hamesucken. Despite Scots law not having statutory offences for loads of common England & Wales ones it is one of the few Scottish offences that doesn't have an equivalent in England & Wales.
Personally I quite like the former Scottish approach of letting offences develop via court rulings rather than knee jerk reactions creating dozens or hundreds of new offences every parliament.