Are you just dropping it in there? You definitely want to use feeding tongs and entice the snake. Make sure it's a little warm to the touch, like a mouse would be. Feed in the enclosure, don't take her out, it will just stress her out, and she'll be less likely to eat, and you're also more likely to get bit.

A lot of people wait a week to try to feed after getting a new baby, just so they get used to their new enclosure. I was able to feed mine only 4 days after I got her though. How are your temps and humidity? Can you describe your set-up?