Yeah, I would add the holes. Just put her in a temporary enclosure where she will feel secure while you drill / solder.

As far as feeding goes, there's no exact science; it's mostly experimentation and patience. Braining the mouse may work, trying a different color or gender of mouse may work, try dangling it with tongs, then leaving it in the enclosure overnight, etc. I prefer feeding a few live meals to new snakes before trying to convert them to f/t, just to be sure they've got some sustenance for the time that it may take to convert.