Can my wife sell her art (paintings) on a Stamp 3?

My wife does a fair bit of painting, and would like to try and sell some of her art (for cash) at one of the many markets here in the south of the country. She is on a Stamp 3, and I'm on a Stamp 1.

Would this be legal for her to do, both from a Revenue and Immigration point of view?

Thanks!

On Stamp 3 she cannot be engaged in any sort of job / business.