There used to be a forum member who posted a lot named rjessome. She is an immigration consultant, and her advice for people in similar circumstances was to just list the job in your employment history, mention it when needed (for example, as part of your history of how you met), and do not go into details about the legality of it. She said that in general the visa officers would not care if someone was working while on a student visa, as long as all other indications were that the relationship is genuine. That is, if the relationship seems to be fake, then working without the proper documentation might be used to bolster their reasons for refusal.