I usually watch closely for 10-20 minutes depending, but some may feel thats too long, while the mouse runs around in my snakes enclosures. If they don't take it in that time period then I put the mice/rats away until the next scheduled feeding day (every 7 days).

You want to get your snake on a 5 day feeding schedule, offer the food to her on Monday and then if she doesn't take it, put it away until the next scheduled day.