I'd go ahead and start increasing her solids so that she's closer to 32 oz per day, which is what's usually recommended for a baby that age. Formula will still be her main source of nutrition, but 40 oz is a lot. You can either cut a bottle or cut down the amount in each bottle, it's really up to you. And of course, if the increase in solids and decrease in formula isn't working for her, there's absolutely nothing wrong with going back up to 40 oz. 32 oz is just an average, and some babies are just hungrier than others!