I would take some extra insulin if you’re seeing it persist for a few days at a time. Many recommend pumping extra insulin and feeding lows if necessary, but I agree with Sarah that if it’s just trace or small, it’s nothing to worry about, per se. Increase your fluids and just keep a close eye for anything moderate to large, I’d say.
We do have a member here whose daughter has been DKA something like eleven times during the few days (PMS) before her cycle begins though, so it’s not a bad idea to suggest that you increase basal by a modest increment at certain times of the month if you start noticing a pattern. I, too, notice trace ketones when I’m pre-menstrual, but until that member brought it up, I’d never thought to check. I don’t change my basals (just do corrections), but I do test for ketones then.