A 32-year-old woman from Mumbai attends the family planning clinic with her husband. She has been on combined oral contraceptive pills (30 μg ethinyl estradiol + levonorgestrel) for the past 4 years with good compliance and no side effects. She is now on day 18 of her current cycle when she develops acute gastroenteritis with severe diarrhoea (6–8 stools per day) lasting 3 days. She is concerned about contraceptive failure. She has no other medical conditions, is a non-smoker, and takes no other medications. What is the most appropriate counselling and management regarding her contraceptive efficacy?