it depends on the age and size of your snake. If she is a baby, she needs to eat something after 3 weeks. If she is older and of a good weight, she can go a few weeks without eating. I made my female switch to rats, she only skipped one meal. What I did was I thawed the rat in the same bowl with a mouse, then rubbed the mouse all over the rat. FIrst time, no go. Second time, she was hungry and she took it straight away. That's pretty fast for a switch, but it does happen. she hasn't looked back. Try to scent the rat with the mouse, that should help some. Also being really hungry is to your advantage. A couple of mine don't like the food right in their face, so if she is like that, just try not to overwhelm her with it. If you want, you can actually leave it in overnight as well. Good Luck