Watching the college World Series, I saw at least two examples of 2B covering 1B on the bunt, and then failing the catch the ball. I've seen it plenty more times with people who aren't Div I players from the best teams in the nation. Assuming your 1B is there because she can catch well, and a reasonably quick P, C, and 3B, I'd leave 1B back most of the time. Why take what should be one of your best gloves and do little more than put her in the way of the 3B or C trying to make a throw? The only real vulnerability is a bunt within 2-3 feet of the 1B line. Sure, there are some bunters who can do that some of the time, but rarely with consistency, and rarer still with a pitch over the inside part of the plate.