Strictly speaking in most countries, it isnt. But an argument can be made that "the vast majority wouldnt be aware that this was against the law" Prosecutors can always elect not to file any charges or lay fines, the courts can always elect to be lenient and not impose any penalty especially when theres any lack of intent or harm. If she had knocked someone down riding it, that would be a different story.

The law will not reference ridable electric suitcases specifically but "motorised ridable vehicles caipable of speeds in excess of 10km/h or with a rated power of more than 500W" (for example) to prevent people from saying "Its not a motorcycle officer, you can clearly see its a suitcase"

Do you know every law in your country / state / province? Honestly you're going to be ignorant of some law, somewhere, especially laws you've never heard of or thought of as a concept.

This is part of what mens rea was supposed to address, but I guess everyone likes to prosecute for the sake of being punitive.

We're yet to see if it's a good one.